lördag 9 april 2011

New Physics, new particles, new forces?

This is a collage of comments and research on the fifth force during latest years. They are not mine, I have only collected these bits of information merely for my own understanding, and maybe now also yours...

These are the pictures stirring up the physics community.

This is the picture creating the storm. The blue peak at MJJ = 145 GeV is not predicted by the standard model.

There is a huge continuum background from W bosons produced with two jets. At the Tevatron, these jets typically come from radiation off the incoming quarks. Here is the distribution before background subtraction:
A possibility is that this is just a mismodeling of the main background, the W+jets "green" component above. So we'll look at the background too. This is a small sample, after all.

This is from Phil Gibbs in viXra blog. A trial to connect more points.

Tommaso: The signal isolated in Run 2. The inset shows the (dijet) excess over background predictions, while the larger distribution is the dijet mass of event candidates. The smallness of the signal contribution highlights how difficult it is to convince ourselves that the signal is true!

Kea: DZERO could not search for hadronic Z boson decays in Run 1, but they did it successfully in Run 2. With a similar technique to the one used by us in CDF, DZERO extracted a signal from xxx inverse picobarns of data. You can see the signal as the black circles in the graph on the right, which is a background-subtracted distribution. As far as I remember, DZERO never published this signal. A public note is available here.

What is the new physics looking like? Let's guess. This is not the first time CDF presents an anomaly.

The 2008 CDF anomaly.
The CDF collaboration presented a set of studies of multi-muon events 29.10.2008. This study was motivated by the presence of several inconsistencies that affect or affected measurements of the b¯b production at the Tevatron. The study is extended to additional properties of multi-muon events. Events in which both muon candidates are produced inside the beam pipe are successfully modeled by known QCD processes which include heavy flavor production. In contrast, we are presently unable to fully account for the number and properties of the remaining events,.At least one of the muon candidates is produced outside of the beam pipe of radius 1.5cm. Cosmic Variance John Conway talks of Ghost Muons: Did CDF underestimate the rate of background processes leading to this sort of observation?
A paper describing a subsample of proton-antiproton collision events in which there is at least one muon produced far from the primary proton-antiproton interaction. This subsample is not yet described by known processes. There can be several muons whose direction of travel lies within 37 degrees of the primary (highest energy) one, and the distribution of muon “impact parameters” has a long tail, out to several centimeters. The impact parameter is a measure of how far away from the main event vertex the particle was produced, and so these extra muons appear to come from the decay of some sort of particle with a lifetime much longer than that of the b quark.

The subsample in question came to light in the course of the measurement of the b quark pair production cross section, which is proportional to the rate at which events with a b quark and a b antiquark are produced. This measurement is done in at least two ways. Unlike the lighter quarks, the b quark lifetime is long enough that it flies a few millimeters through space before decaying. So in one method, one looks for “secondary vertices”, distinct from the primary location in space where the proton and antiproton collided. These secondary vertices are where the b quarks decay to several hadrons, or possibly leptons such as muons.
The b quark decays to muons offer another way to measure not only the pair production cross section but the “mixing” of b quarks. Due to a subtlety in the weak interaction that we need not explore here, a b quark (or more properly speaking a B hadron) flying along can change spontaneously into its own antiparticle.
If one selects events with two muons, but tighten the previously used requirements on where the muons come from, demanding that they emanate from near the main event vertex, they find much better agreement between the two different measurements of the b pair cross section. But this implies that the previous measurements suffered from a large, unaccounted-for background. What is it?
Let's look at the pictures from then.

Picture: the impact parameter distribution of muons in the events constituting the anomalous signal (black points), compared to the impact parameter of muons attributable to QCD sources (in red). The impact parameter resolution for these tracks is 2.5 times smaller than the bin size. One observes a abnormal tail of muons with very large impact parameter. I recall that the impact parameter, which is measured in the plane transverse to the beam direction, is the distance of closest approach of the backward extrapolation of the track to the primary interaction vertex. A impact parameter of one centimeter is huge, given that the typical decay length of a B meson is of the order of a pair of millimeters.

An exponential fit to the impact parameter distribution of the trigger muons for the anomalous events, for events with just two (top) or more than two (bottom) muons inside two narrow cones around the trigger muons. The distribution agrees with the decay of a particle with a lifetime in the 20 picosecond range.

The background.
John Conway: The paper is an exploration of this ghost background, and the conclusion is that we can’t explain it at this point. So the collaboration has published what we’ve learned so far, in hopes that other experiments, especially our neighbors around the ring at D0, can look at their data and tell us if they see this sort of thing too. This is the most important first question to be answered, and if they do see it, I can tell you what will happen: all hell will break loose in the field.

Francis the Mule (why such a name?) has in spanish an article, possible explanation of multi-muons...

Giromini et co. member of CDF, (0810.5730) look at the phenomenological picture of the background suggested by the topology and kinematic properties of the multi-muon events. The electroweak symmetry breaking sector in the SM Lagrangian appears to be the most elusive and the one most likely to provide experimental surprises. The salient features of the data could be accounted for by postulating the pair production of three new states h1, h2, and h3 with masses in the range of 15, 7.3, and 3.6 GeV/c2, respectively. The heavier states cascade-decay into the lighter ones, whereas the lightest state decays into a pion pair with a lifetime of the order of 20 ps. Let's look at some of the pictures:
Sign-coded multiplicity distribution of additional muons found in a cos angle ≥ 0.8 cone around the direction of a primary muon in ghost events. The solid line is the prediction of the toy-simulation of a decay into eight pion leptons. See article.

Invariant mass, M, distribution of (left) all muons and (right) all tracks with pT ≥ 2 GeV/c for events in which both cones contain at least two muons. QCD and fake muon contributions have been removed. See article. Note, no additional peak. Sorry for the bad quality.

The rate and kinematic properties of tracks and muons contained in a 36.8◦ cone around the direction of each trigger muon in ghost events; initial muon pairs is markedly different from that of QCD events, the rate of additional muons and charged tracks is significantly higher than that of QCD events. The mechanism that produces h1 pairs is completely obscure. It does not appear to be resonant nor mediated by a photon or gluon exchange. The observed pair production cross section (c. 100 nb) is a few orders of magnitude larger than what is predicted if the hn states belonged to the Higgs sector.

Distributions, reproduced from CDF, of the invariant mass, M, of three-track systems in ghost events. Ghost events with positive Lxy exhibit an excess of events with the expected shape of pion into three hadron decays.

Ellwanger 2010 still tries to fit it to Higgs: In the Next-to-Minimal Supersymmetric Standard Model, CP-even Higgs bosons can have masses in the range of 80-110 GeV in agreement with constraints from LEP due to their sizeable singlet component. Nevertheless their branching ratio into two photons can be 10 times larger than the one of a Standard Model Higgs boson of similar mass due to a reduced coupling to b quarks. This can lead to a spectacular enhancement of the Higgs signal rate in the di-photon channel . By asymmetry.
In aug 2009 in a phenomenology NMSSM pic: presence of a light pseudoscalar, the SM-like Higgs scalar can decay dominantly into a 4-tau final state. Susy used.

Phenomenological study of the atypical heavy flavor production, Apollinari et.al. (hep-ex/0511053) 2005:
known discrepancies between the heavy flavor properties of jets produced at the Tevatron collider and the prediction of conventional-QCD simulations. In this study, we entertain the possibility that these effects are real and due to new physics. We show that all anomalies can be simultaneously fitted by postulating the additional pair production of light bottom squarks with a 100% semileptonic branching fraction.
CDF Multi-Muon Events and Singlet Extensions of the MSSM, Domingo & Ellwanger, jan.2009.
We discuss a generalization of the minimal supersymmetric extension of the Standard Model in the form of three additional singlet superfields, which would explain the essential features of the CDF multi-muon events presented recently.
John Conway (a CDF member): If this is the first observation of some sort of new physics, then it is tremendously exciting and very, very weird. Though, oddly, not entirely unanticiapted. Neal Weiner and Nima Arkani-Hamed have a paper out where they predicted “lepton jets” not unlike what we are seeing. Kind of makes the hair stand up on the back of your neck… Comment from Weiner: Our statement about lepton jets wasn’t just about production of the vector itself, because typical decays through the G_dark sector don’t go right to the vector, but proceed through some intermediate states, hence the c.=2 rather than n=2 definition of the lepton jets…

See Tommasos chat with Arkani-Hamed (and Weiner) (see at bottom). Arkani-Hamed talks of dark matter, but I will take it later, because the new finding has exaggerated the discussion toward DM. First the 2011 anomaly.

The explanation? None.
"A component not explained" is less than exciting; however, the peculiarities of the sample of events unearthed by CDF did lend itself to speculate that the Standard Model would soon crumble under its own weight, yielding in a way that was unexpected -that is, in the modeling of the lifetime of observed muons in hadron collisions. A detailed explanation in four parts of the results of the CDF study is available at the following links: part I, part II, part III, part IV. I also took the time to study in some more detail than I had so far the theory of a "Hidden Valley", of which the CDF signal might appear to be a signature. And my opinion slowly changed. However, I felt I had not really insulted anybody with my outing on October 31st, 2008, so I let the story die out. As for the CDF anomaly, the issue is still open. True, DZERO did publish a conference proceedings where they claim to not see any excess of muons with large impact parameter in a dataset similar to the one where CDF sees a large one. However, there are a few things that make me doubt that the DZERO analysis is a conclusive rebuttal of the CDF signal, primum inter pares the fact that DZERO has a tracking efficiency that dies out quickly for tracks not pointing toward the primary vertex.

Flesh and Blood, or Merely Ghosts? Some Comments on the Multi-Muon Study at CDF, by Strassler nov, 2008.
Despite its tenuous nature, this hint highlights the experimental difficulties raised by such signals, and merits some consideration. Some of the simplest interpretations of the data, such as a light neutral particle decaying to muon and/or tau pairs, are largely disfavored; three-body decays to \tau\tau\nu appear slightly better. An alternative speculative possibility - a "micro-cascade decay" - might be consistent with the data.
...in which a new hidden sector with a mass gap is added to the standard model and coupled to it at or below the TeV scale, naturally predicts high-multiplicity production of new neutral states, which are potentially very light, and are typically long-lived, possibly decaying with macroscopically displaced vertices. Unparticle models with mass gaps are examples of hidden valleys as is a recent model of darkmatter. No serious attempt is made to interpret the data...forthcoming searches at the Tevatron and the LHC.

...displaced vertices from the decay of new neutral particles...
New Evidence for Colored Leptons,by Matti Pitkänen 2008.
The recent discovery of CDF anomaly suggest the existence of a new long-lived particle which means a dramatic deviation from standard model. This article summarizes the quantum model of CDF anomaly. The anomaly is interpreted in terms of production of τ-pions which can be regarded as pion like bound states of color octet excitations of τ-leptons and corresponding neutrinos. Colored leptons are one of the basic predictions of TGD distinguishing it from standard model.
Axions at LHC, 2009, by Guzzi. A bottom-up approach.
The most simple and appealing extensions of the Standard Model are those in which the SM gauge group is enlarged by multiplying it by one or several extra U(1) abelian gauge groups. In these extensions, the extra abelian symmetry naturally gives rise to extra neutral currents (Z′). Some particular low energy realization of string theories (D-brane models) are anomalous, and in the presence of a specific type of scalar potential, they predict the existence of a physical axion. A picture of a tripartite/circular loop is shown.

All renormalizable couplings are included as well as some dimension-five couplings that are important, in the context of the Wess-Zumino mechanism, to restore the gauge invariance in the general case. As a matter of fact, gauge invariance requires the presence of an axion that appears as an asymptotic state.

On the basis of some recent discussions on multi-muon events observed at the Tevatron (see Ellwanger et.al. 0812.1167[hep-ph], Giromini et.al.), one might wonder whether the production of a light pseudo scalar particle is a possible candidate for the explanation of such events. As a matter of fact, in the MLSOM, the production cross section for a light pseudo-scalar particle through the gluon-gluon fusion channel has a large value, due to the structure of its coupling to the fermions and to the fact that the gluons are singular when the virtuality in the s channel is low.
with: 'Axions from Intersecting Branes and Decoupled Chiral Fermions' at the Large Hadron Collider, Claudio Corian`o and Marco Guzzi.
Using considerations based on its lifetime, we show that in brane models the axion can be dark matter only if its mass is ultralight (c. 10−4 eV), while in the case of fermion decoupling it can reach the GeV region, due to the absence of fermion couplings between the heavy Higgs and the light fermion spectrum.
High energy PhD's. That crazy leptonic sector febr 2009: The CDF multi-muon anomaly has been an experimental curiosity for a few months now, but it seems to have taken a back seat to PAMELA/ATIC for `exciting experimental directions’ in particle phenomenology. The end of 2008 for hep-ph‘ists (the associated initial model-building attempt 0811.1560 Strassler.) was marked by three interesting leptonic signals. The CDF multi-muon anomaly, PAMELA/ATIC (0812.4457, 0902.0376), and the MiniBooNE excess (not much is said).

Multiple members of the CDF collaboration refer to the multi-muon publication as "that crap" (when being polite), while those who signed it admit the fact with certain embarrassment.

The CDF anomaly 2011.

CDF finds evidence for top quark production asymmetry, Fermilab Today Jan, 7. A new analysis at Fermilab points to an asymmetry in top quark production. This analysis raises the asymmetry of forward and backward top quark production found in a 2008 analysis to a ~3 sigma level. This analysis was performed for the first time in 2006 at CDF. CDF and DZero both published their inclusive analysis of this asymmetry in 2008. Fermilab’s Tevatron produces collisions that create top quark and anti-top-quark pairs via the strong force. This result shows that nature prefers an imbalance that is even larger than predicted (6%?). For Mttbar> 450 GeV/c2the asymmetry is measured to be 48 ± 11 percent, three standard deviations from Standard Model expectation (9 ± 1 percent).

A discrepancy in the symmetry predicted by theories of the Standard Model can point to new types of physics, an anomaly in the data or that the current theories need revision.

The CDF experiment at the Tevatron proton-antiproton collider caused a stir with this paper and a special seminar 6.4.2011.
A bump like this could be a sign that a new particle (a bit like the W boson but nearly twice as massive) was made, and deacyed to two jets. There is no such particle known to science.

Resonaance: All in all, the excess advertised in today's CDF paper is not exactly new, and it has been widely discussed among theorists. Moreover, the analysis published today has been publicly available for some time in the form a PhD thesis. What changed with respect to the earlier CDF diboson search is that the cuts have been slightly revamped to make the bump more pronounced.

Z prime boson?
The simplest explanation, proposed in this April Fools' paper, involves a 150 GeV Z' boson. A light Z' with a significant coupling to leptons is excluded by LEP and the Tevatron, but if the coupling to leptons is small then the limits are surprisingly weak. In particular, 150 GeV Z' with electroweak size couplings to quarks is perfectly allowed, and would have the right cross section to produce a bump observed by CDF. One should note that Z' with the mass of that order could generate a large forward backward asymmetry of the top production, as observed in another CDF analysis. But one should also note that generating the asymmetry requires a large flavor violating coupling u t Z' which in principle is not related to the coupling to the light quarks that is probed by today's CDF paper. see Flip, Tommaso, Sean, and Michael, Peter, Lubos, and again Tommaso.

Light Z' Bosons at the Tevatron 1103.6035, Buckley et co. 1.4.2011.
A Z' boson with suppressed couplings to leptons, however, could be much lighter and possess substantial couplings to Standard Model quarks... a new leptophobic Z' gauge boson as a simple and well motivated extension of the Standard Model..three of the recent anomalies reported from the Tevatron - in particular the top-quark forward-backward asymmetry and excesses in the 3b and W + 2 jets final states - could be explained by a new Z' with a mass of approximately 150 GeV, relatively large couplings to quarks, and suppressed couplings to electrons and muons. Moreover, we find that such a particle could also mediate the interactions of dark matter.

A Z' Model for the CDF Dijet Anomaly, by Felix Yu, 2011. We find that the 145 GeV broad feature seen by CDF in the dijet invariant mass distribution can be explained by a Z' boson that couples only to first generation quarks. (See also 1104.1375 Tevatron Wjj Anomaly and the baryonic Z′ solution, Cheung & Song., also arXiv:1104.1161, arXiv:1104.0976)

Others say this model cannot be true. Universal Z/ models that could explain the CDF anomaly are excluded.

Technipion,Compton wavelengths and scaled up leptons?
Technicolor at the Tevatron Eichten et co. 6.4.2011: technipion\pi_T of low-scale technicolor.Its relatively large cross section is due to production of a narrow Wjj resonance, the technirho, which decays to W + \pi_T. We discuss ways to enhance and strengthen the technicolor hypothesis and suggest companion searches at the Tevatron and LHC. Low-scale technicolor is the \Rosetta Stone" of electroweak symmetry breaking?

Discovering technicolor, Andersen et co. 7.4, 2011: Higgs is composite, dynamical electroweak symmetry breaking, Technicolor. Motivations, constructions, underlying gauge theories leading to minimal models of Technicolor, the comparison with electroweak precision data, the low energy effective theory, the spectrum of the states common to most of the Technicolor models, the decays of the composite particles and the experimental signals at the Large Hadron Collider, establish the relevant experimental benchmarks for Vanilla, Running, Walking, and Custodial Technicolor, and a natural fourth family of leptons.

Sidharth, 2011: Consequences (from high energy runs at LHC) like a possible new shortlived interaction within the Compton scale.
Both the positive and negative energy solutions are required to form a complete set and to describe a point particle at x0 in the delta function sense. The narrowest width of a wave packet containing both positive and negative energy solutions, which describes the spacetime development of a particle in the familiar non-relativistic sense, as is well known is described by the Compton wavelength. As long as the energy domain is such that the Compton wavelength is negligible then our usual classical type description is valid. However as the energy approaches levels where the Compton wavelength can no longer be neglected, then new effects involving the negative energies and anti particles begin to appear.
From the super position of states principle leads to the matrix Hıj(t) identified with the Hamiltonian operator, and to the Schrodinger equation (obs. time). If we approach distances of the order of the Compton wavelength, the negative energy solutions begin to dominate, and we encounter the well known phenomenon of Zitterbewegung.

TGD 2011. Is a scaled up copy of hadron physics in question? Is the new boson reported by CDF pion of M89 hadron physics? Also colored excitations of leptons and therefore leptohadron physics are predicted.

The natural explanation for preference of quark pairs would be that strong interactions are somehow involved. This suggests a state analogous to a charged pion decaying to W boson and two gluons annihilating to the quark pair (box diagram). This kind of proposal is indeed made in Technicolor at the Tevatron and has as its analog second fundamental prediction of TGD that p-adically scaled up variants of hadron physics should exist and one of them is waiting to be discovered in TeV region. This prediction emerged already for about 15 years ago. Mersenne primes define fundamental mass scales (see this).

What is amusing that CDF discovered towards the end of 2008 what became known as CDF anomaly giving support for tau-pions. The evidence for electro-pions and mu-pions had emerged already earlier (for details see the link above). All these facts have been buried underground because they simply do not fit to the standard model wisdom. TGD based view about dark matter is indeed needed to circumvent the fact that the lifetimes of weak bosons do not allow new light particles. TGD indeed predicts p-adically scaled up copy of hadron physics in TeV region and the lightest hadron of this physics is a pion like state produced abundantly in the hadronic reactions. Ordinary hadron physics corresponds to Mersenne prime M107=2107-1 whereas the scaled up copy would correspond to M89. The mass scale would be 512 times the mass scale 1 GeV of ordinary hadron physics so that the mass of M89 proton should be about 512 GeV.
About Octonions. 0,89 x 512 = c. 450, which is the predicted value acc. to Jessie Shelton. Likely heavy: m c. 500 GeV, leptophobic, not obviously related to electroweak symmetry breaking.
Of course, anything coupling to t¯t will be produced at a linear collider at some level: ...but rates may be low. A loop is produced.

2008. Third-generation fermions are challenging but potentially very rewarding:
sensitivity to spin, mixing, chiral structure. Shelton & Zurek, 2011: A Theory for Maximal Flavor Violation.
... a case for flavor violation which maximally mixes the first and third generation flavors. As an example, we realize this scenario via new right-handed gauge bosons, which couple predominantly to the combinations (u,b)_R and (t,d)_R. We show that this new flavor violation could be responsible for several anomalies, focusing in particular on the B_d and B_s systems, and the Tevatron top forward-backward asymmetry.

Resonaances 31.10.08, a question in the comments: Can anyone explain why the CDF anomaly has to be linked to the poorly understood physics of Dark Matter? Are there any hints that strongly support this connection?

If dark matter is thermal weakly interacting massive particles (WIMPs) then it may produce observable signals when it self annihilates. A popular model for the WIMP which would self annihilate is the neutralino (see figure). Self annihilation is exactly what it sounds like, like two identical but opposite forces meeting, the result is an explosion of energy and particles (the interaction conserves energy, momentum, and other quantum numbers). WIMP self annihilations into positrons and electrons could be detected by cosmic ray detectors.

The anomaly occurs in a theoretically difficult region, the B-baryon spectrum is poorly known, the local Monte Carlo magicians are very sceptical about modeling the b-quarks, etc, etc. And Jester points to this paper, SuperUnified Theory of Dark Matter. The visible and dark sektors have different scales for symmetrybreaking. For this they started to already talk about a Nobel.
The dark matter particle that is charged under the dark group and has a large mass; unlike in a typical MSSM-like scenario, dark matter is not the lightest supersymmetric particle. The dark group talks to the MSSM (visible group) thanks to a kinetic mixing of the dark gauge bosons with the Standard Model photon, that is via lagrangian terms; the dark group is U(1), although for non-abelian gauge groups there is a way to achieve that too (via higher-dimensional operators). Once the dark gauge boson mixes with the photon, it effectively couples to the electromagnetic current in the visible sector. Thanks to this mixing, the dark gauge boson can decay into the Standard Model particles. The SuperUnified model is tailored to fit the cosmic-ray positron excess PÀMELA and ATIC/PPB-BETS. The dark matter particle with a TeV scale mass is needed to explain the positron signal above 10 GeV (as seen by PAMELA) all the way up to 800 GeV (as suggested by ATIC/PPB-BETS), see here. The dark gauge bosons with a GeV mass scale play a two-fold role. Firstly, they provide for a long range force that leads to the Sommerfeld enhancement of the dark matter annihilation rate today. Secondly, the 1 GeV mass scale ensures that the dark matter particle does not annihilate into protons/antiprotons or heavy flavors, but dominantly into electrons, muons, pions and kaons. Supersymmetry does not play an important role in the dynamics of dark matter, but it ensures "naturalness" of the 1 GeV scale in the dark sector, as well as of the electroweak scale in the visible sector. I guess that analogous non-supersymmetric constructions based, for example, on global symmetries and axions will soon appear on ArXiv.
In neutrino research the darkmatter particle has indeed been found to be very heavy. Jester continues:
What connects of this model to the CDF anomaly is the prediction of "lepton jets". In the first step, much as in the MSSM, the hadron collider produces squarks and gluinos that cascade down to the lightest MSSM neutralino. The latter mixes into the dark gauginos, by the same token as the dark gauge boson mixes with the visible photon. The dark gaugino decays to the dark LSP and a dark gauge boson. Finally, the dark gauge boson mixes back into the visible sector and decays into two leptons. At the end of this chain we obtain two leptons with the invariant mass of order 1 GeV and a small angular separation.
Nima Arkan-Hamed & co has also written an interesting paper 2008, 'A theory of dark matter.'
Cosmic ray spectra from ATIC and PAMELA require a WIMP with mass M_chi ~ 500 - 800 GeV that annihilates into leptons at a level well above that expected from a thermal relic. Taken together, we argue these facts imply the presence of a GeV-scale new force in the dark sector. The long range allows a Sommerfeld enhancement to boost the annihilation cross section as required, without altering the weak scale annihilation cross section during dark matter freezeout in the early universe. If the dark matter annihilates into the new force carrier, phi, its low mass can force it to decay dominantly into leptons. If the force carrier is a non-Abelian gauge boson, the dark matter is part of a multiplet of states, and splittings between these states are naturally generated with size alpha m_phi ~ MeV, leading to the eXciting dark matter (XDM) scenario previously proposed to explain the positron annihilation in the galactic center observed by the INTEGRAL satellite. Somewhat smaller splittings would also be expected, providing a natural source for the parameters of the inelastic dark matter (iDM) explanation for the DAMA annual modulation signal. Since the Sommerfeld enhancement is most significant at low velocities, early dark matter halos at redshift ~10 potentially produce observable effects on the ionization history of the universe, and substructure is more detectable than with a conventional WIMP. Moreover, the low velocity dispersion of dwarf galaxies and Milky Way subhalos can greatly increase the substructure annihilation signal.
Spectrum of exciting dark matter gives asymmetry.

Picture: Contours for the Sommerfeld enhancement factor S as a function of the mass ratio m -phi/m-x and the coupling constant λ, σ = 150 km/s (right). Left Sommerfeld enhancement factor R dito, vrms = 10 km/s. A possible effect on the polarization of the CMB.

Matti P.: Already at seventies (A.T. Goshaw et al (1979), Phys. Rev. Lett. 43,1065) a lot of evidence for colored electrons, or rather their pion like bound states, came from anomalous production of electron positron pairs in heavy ion collisions. So this is not at all anything new. It has been put aside, darkened, as the dark matter boson it is:). I also discuss the possibility that this process requires a phase transition increasing Planck constant. If so -as the argument suggests- then leptopions would represent one instance of dark matter. The extremely important data bit
is that the decays to two jets favor quark pairs over lepton pairs.
The surprising finding of PAMELA is that positron fraction (the ratio of flux of positrons to the sum of electron and positron fluxes) increases above 10 GeV. If positrons emerge from secondary production during the propagation of cosmic ray-nuclei, this ratio should decrease if only standard physics is be involved with the collisions. This is taken as evidence for the production of electron-positron pairs, possibly in the decays of dark matter particles.

Is the new boson reported by CDF pion of M89 hadron physics?
Neutral pions produce monochromatic gamma pairs whereas heavy charged pions decay to W boson and gluon pair or quark pair. The first evidence -or should we say indication- for the existence of M89 hadron physics has now emerged from CDF which for more than two years ago provided evidence also for the colored excitations of tau lepton and for leptohadron physics. What CDF has observed is evidence for the production of quark antiquark pairs in association with W bosons and the following arguments demonstrate that the interpretation in terms of M89 hadron physics might make sense.
The predicted exotic octet of gluons proposed as an explanation of the anomalous backward-forward asymmetry in top pair production could actually correspond to the gluons of the scaled up variant of hadron physics. Could it be that given Mersenne prime tolerates only single hadron physics or leptohadron physics? In the collision incoming quark of proton and antiquark of antiproton would topologically condense at M89 hadronic space-time sheet and scatter by the exchange of exotic octet of gluons: the exchange between quark and antiquark would not destroy the information about directions of incoming and outgoing beams as s-channgel annihilation would do and one would obtain the large asymmetry.

Darkogenesis: A baryon asymmetry from the dark matter sector, Jessie Shelton and Kathryn M. Zurek, Phys Rev. D. oct. 2010:
In standard models of baryogenesis and of dark matter, the mechanisms which generate the densities in both sectors are unrelated to each other. In this paper we explore models which generate the baryon asymmetry through the dark matter sector, simultaneously relating the baryon asymmetry to the dark matter density. In the class of models we explore, a dark matter asymmetry is generated in the hidden sector through a first order phase transition. Within the hidden sector, it is easy to achieve a sufficiently strong first order phase transition and large enough CP violation to generate the observed asymmetry. This can happen above or below the electroweak phase transition, but in both cases significantly before the dark matter becomes non-relativistic. We study examples where the Asymmetric Dark Matter density is then transferred to the baryons both through perturbative and non-perturbative communication mechanisms, and show that in both cases cosmological constraints are satisfied while a sufficient baryon asymmetry can be generated.

If the dark phase transition occurs above the electroweak phase transition, a generated dark asymmetry can be communicated to the SM via electroweak sphalerons, instead of through higher dimension operators. This mechanism requires the introduction of messenger fields which carry both SU(2)L and U(1)D quantum numbers, such that U(1)D becomes anomalous under SU(2)L. We will call these chiral messengers leptodarks, as in our model they will have lepton-like SM charges, in addition to carrying dark number.

No one seems to have noticed the appearance of (essentially 5 sigma) new physics (eg. at MINOS), the first direct observation of muon antineutrino disappearance consistent with oscillation, yielding the most precise measurement to date of the larger antineutrino mass-squared difference.. The MINOS muon neutrino and muon antineutrino measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters, neutrinos passing through matter could experience non-standard interactions that alter the masses.

Too little CQD?
The other extreme of asymmetry is raported too, mass disappering. Domingo et co., 2009: Bottomonium spectroscopy with mixing of eta_b states and a light CP-odd Higgs,
The mass of the eta_b(1S), measured recently by BABAR, is significantly lower than expected from QCD predictions for the Upsilon(1S) - eta_b(1S) hyperfine splitting. We suggest that the observed eta_b(1S) mass is shifted downwards due to a mixing with a CP-odd Higgs scalar A with a mass m_A in the range 9.4 - 10.5 GeV compatible with LEP, CLEO and BABAR constraints. We determine the resulting predictions for the spectrum of the eta_b(nS) - A system and the branching ratios into tau^+ tau^- as functions of m_A.

After all the QCD is still not so very much explored.

At last:
Nima Arkani-Hamed
on Tommasos blog - November 3, 2008: It was stimulating to see the CDF paper. However, this is an extremely challenging analysis, and many further cross-checks will have to be done to take it as a serious indication for physics beyond the standard model. We are all well aware that particle physics anomalies have come and gone in the past two decades, in analyses that are less complicated than this one; of course the collaboration made no claim to have discovered new physics. Keeping this in mind, let me first make comments on some physics I have been involved with, and end with some comments on sociology.

I have been working recently with Doug Finkbeiner,Tracy Slatyer and Neal Weiner on a theory for dark matter motivated by a growing number of anomalies in astrophysics, most recently PAMELA/ATIC.
This work is a direct continuation of (in my view) beautiful earlier work pioneered by Neal, Doug and Dave Tucker-Smith, who have collectively pushed it for many years. In fact, Neal, Doug and others previously talked about GeV scalars decaying to leptons in the context of “exciting” dark matter, to explain the INTEGRAL signal, as well as the HEAT excess predecessor to PAMELA. So the idea of GeVish mass particles decaying to leptons, motivated by Dark Matter anomalies, goes back to Feb 2007–Feb 2008. See e.g. astro-ph/0702587 and especially arXiv:0802.2922.

What we did in our four author paper was to show that all these strands fit together into a simple unified picture that also makes very good particle physics sense. The idea can be summarized in one sentence: Dark Matter is charged under a non-Abelian gauge symmetry broken at the GeV scale. We pointed out two additional major motivations for the GeV scale–first, the new vectors with this mass naturally “Sommerfeld enhance” the annihilation cross section as appears necessary to explain the PAMELA/ATIC signals from DM annihilation; second, the broken gauge symmetry at the GeV scale radiatively induces splittings between the different states in the DM multiplet at the \sim MeV scale, which is precisely what is needed in “exciting” and “inelastic” DM explanations of the INTEGRAL and DAMA signals. All of these phenomena, scattered over energy scales ranging from a TeV to an MeV, are essentially a consequence of the single sentence I used to describe our picture above. We find this compelling.

Since the GeV gauge sector is non-Abelian, there are a number of states, minimally including vectors and higgses, all GeVish in mass. One thing that happens when at least some of these GeV particles are vectors is that they can easily talk to the Standard Model, via kinetic mixing with the photon. The mixing is naturally small, so directly producing this particle is challenging–though people have talked about doing it at low-energy e+ e- machines (B-factories,
DAPHNE, BESS). Neal and I considered the simplest marriage of our DM picture with low-energy SUSY, which further naturally generates the GeV dark gauge symmetry breaking scale. We also pointed out that in this set-up, one could produce particles in this new GeV sector much more copiously, not directly, but indirectly through SUSY production: every SUSY event will end with MSSM LSP’s which then decay into the true LSP in the dark sector; essentially all of these will also be accompanied by some of the GeVish particles that re-decay back into SM leptons. One would expect a cascade of decays in the GeV sector given the multiplicity of states, and thus the aptly named “lepton jets”. We discussed displaced vertices as a possibility, though they are not guaranteed. So, seeing “lepton jets” as an O(1) fraction of SUSY signals is what we talked about as the smoking gun of our model at the LHC. It would indeed be an amazing signal, which is why we were and continue to be very excited about it!

Now, even if the CDF anomalies are an indication of new physics–which I think in all of our views is _very_ far from obvious– it can not be due to the signal Neal and I talked about, arising from SUSY cascade decays. The rate of the CDF anomaly is absolutely enormous–you are talking about 70,000 “ghost” events! If there is a connection to our model at all, it would likely have to be through direct production of the GeV sector particles, that still cascade decay in the dark sector and produce the lepton jets. As I mentioned there are limits one can put on this from e+ e- data, and a number of us had been wondering what could be done at hadron colliders, but at least my instinct was that the rates wouldn’t be high enough and it would be far too messy and difficult to extract a signal. We were planning on thinking about this in more detail soon, but the exploration of the consequences of our model is very new, and for now most of us have been focusing on getting out the important predictions on the DM side for GLAST/Fermi, as well as fleshing out the big O(1) LHC predictions. Obviously, stimulated by the CDF result, studying the question of direct production at the Tevatron is much higher on our list of priorities, and we are looking at it now to see if it can even be in the right ballpark. But to re-iterate: even if the CDF anomaly is new physics, and even if it is connected to our model, (and needless to say these are two very big “ifs”), it would be a wonderful surprise to me since I had expected probing direct production of the GeV sector to be incredibly difficult at a hadron collider.

So much for the physics. Turning to the sociology: you publicly suggested that we had gotten wind of the CDF experimental result ahead of time, and casually wrote this paper pointing out the signal before the experimental result was published. Your only evidence is that we made a surprising prediction of a signal experimentalists hadn’t thought of before and put it out before the experimental results were made public–Gasp! Shocking! Scandalous! Never happened in the history of physics! Not contained in the definition of the word “pre”diction! This was a hilariously preposterous accusation; however it stopped being funny when you went further and all but
called Neal a liar when he stated unequivocally that we had no advance knowledge of the CDF result–this is outrageous. As Neal said, we had no knowledge about the experimental result ahead of time _at all_. We didn’t even talk about the Tevatron in our paper! And as I said above, even if this anomaly is real and even if it is related to our model, it can not be literally the signal we talked about. Also, the thought that we could somehow cook up a model motivated by explaining dark matter anomalies as a cover to explain rumored events at CDF is absurd–ask any theorist friends you may have whether this is feasible and you will get a good chuckle out of them. You think this signal “came out of the blue”, but if you have been following any of the developments in BSM collider physics in the past couple of years you will realize that signals involving high particle multiplicities with displaced vertices have been discussed for quite a while–check out the repeated use of the phrase “hidden valley” in my paper with Neal for references to work by Strassler, Zurek et. al. Our contribution is that a rather specific version of such a picture–with the GeV mass scale and coupling to the SM through kinetic mixing with the photon–is naturally singled out by the new picture of dark matter we put forward with Doug and Tracy, giving a potentially exciting connection between what we are now seeing in the sky and what we might see at colliders. As it happens this type of hidden valley model had not been discussed in the literature, so we happily pointed out some of their possibly dramatic LHC consequences. Perhaps if you had bothered to even superficially read our papers and think about the physics, it wouldn’t seem so “out of the blue” to you, and you would understand that these light GeV particles decaying to leptons are a necessary feature of our model of Dark Matter, whether CDF saw any hints for them or not.

I find your cynicism remarkable. We are entering what promises to be a golden era of amazing experiments in high-energy physics, astrophysics and cosmology, which may very well lead to profound advances in our understanding of Nature at a fundamental level. All of us–experimentalists and theorists alike–are fantastically excited about this and are doing everything we can to give it the best chance of happening. And at least most of us don’t think of physics as a soap opera rife with rumor and innuendo, or spend the precious time we have cynically tossing around completely baseless and deeply offensive accusations.

Speaking of precious time, I’m sure you’ll agree that there is more critical physics to do than there are hours in the day to do it, and I for one would like to get back to work.

Nima Arkani-Hamed

13 kommentarer:

  1. http://blogs.uslhc.us/first-cms-results-on-ww-production-and-higgs-search

  2. Den här kommentaren har tagits bort av skribenten.

  3. I got a mail about a recent comment on Tommasos blog The Rumored Rumor Had Been Rumored Before from 13.7.2010.
    This also contained a light bottom dijet.

    I quote.
    Its interesting that the LHC has not been doing any physics for the past 3-4 days, but instead is working on "machine development." They were up to over 780 bunches with 50 ns spacings last week and now they are doing machine development with <10 bunches. I also read CMS had not confirmed the "suspected" Higgs boson peak, which was 30x expectations.

    This is speculation, but its starting to sound a lot like the 30x resonance is an artifact of the machine and the LHC folks are working fevorously to isolate & correct it. Wouldn't it be a dissappointment if more than a year's worth of LHC data is confounded with an machine artifact that is 30 times larger than expected signals of interest?

  4. Tommasos answer:
    wrong thread (this should belong to the discussion about this other rumor, http://www.science20.com/quantum_diaries_survivor/did_atlas_just_see_higgs-78316). But anyway, the schedule of the LHC has nothing to do with what the experiments do or don't do... We are past the times of the Rubbias who could waive their arms and pound their fists until everybody did what he liked.

    In any case the "30x resonance" is not an artifact of the machine, but a simple artifact of statistics.

  5. http://resonaances.blogspot.com/2011/05/more-on-wjj-bump-in-cdf.html

    I don't write the first part of the blogpost. It is mere repetition. then...

    To ease the UA2 constraints one can turn to another class of model. Quite generally, the Tevatron may produce a ≥ 250 GeV mother resonance who decays to a W boson and a 150 GeV daughter resonance. The latter subsequently decays to 2 jets who are observed by CDF. Several proposals for the mother and daughter exist: a technirho meson decaying to a technipion and a W in a version of technicolor, a sbottom decaying to a stop and a W in R-parity violating supersymmetry, a charged Higgs decaying to a neutral Higgs and a W in two-Higgs doublet models, a weak doublet color octet in the Manohar-Wise model, etc. The striking prediction of this class of models is that not only the invariant mass of the jets but also of the entire final state should display a resonance. CDF looked at the invariant mass of the 2 jets + lepton + missing energy vector and found it consistent with background only, but it is not clear if this excludes the presence of a mother resonance (the presence of the missing energy introduces larger systematic uncertainties than for the jet pair mass).

    One can also imagine a more intricate class of models where the lepton and the missing energy in the CDF excess events come not from a usual W boson but from some other particle decaying to an electron and a neutrino. For example, this paper explains the excess by a production of a pair of supersymmetric winos of which one decays, via R-parity violation, to a charged lepton and a neutrino, and the other decays to 2 jets. This possibility may be excluded by analysis the distribution of the transverse mass of the lepton+missing energy subsystem.

    Finally, one should mention those who are trying to spoil the party. From the very beginning many have cast doubts on the CDF analysis as it requires a perfect control over the overwhelming Standard Model backgrounds. One thing is that even the Standard Model W/Z peak in the observed jet mass spectrum, arising due to the well known contribution of the WW and WZ production processes, does not seem to be very well described by the simulations. Furthermore, by eye it seems that shifting the jet energy scale a few percent upwards, which would correspond to shifting the whole data curve to the right, allows one to get rid of the excess (the authors of the analysis reply that raising the jet energy scale makes additional events pass the analysis cuts, so that naive shifting of the curve is not correct; they say a 3 sigma excess persists even when the JES is scaled up by 7 percent). Another attempted explanation is that the apparent excess is in reality the Standard Model top quark. When a top quark decays hadronically, t → W b → jjb, the invariant mass of the 2 light jets of course peaks at the W boson mass of 80 GeV, however the invariant mass of the b-jet and one of the light jets has the distribution peaking near 150 GeV (the endpoint is Sqrt[mTop^2- mW^2] = 155 GeV), suspiciously close to the CDF bump. Thus, the excess may be due to the semileptonic t-tbar or single top production where one or more additional jets are missed at the detector, assuming the Monte Carlo simulations of that background have been (rather grossly) mismodeled.

    So this is where we stand today. The situation may or may not be clarified when more data arrive. The imminent updates from CDF and D0 are top secret and no one outside these collaborations, especially theorists, knows the results ;-) Someone will call a bluff? Or someone is holding an ace up his sleeve? Stay tuned for the next episode.

  6. The signal grows, is now 4,8

    http://blois.in2p3.fr/2011/transparencies/punzi.pdf CDF update

    Matti has also commented

  7. http://matpitka.blogspot.com/2011/06/simplest-identification-of-150-gev.html

  8. http://www.wired.com/wiredscience/2011/06/dzero-non-result/
    When the CDF collaboration analyzed collisions between a proton and an antiproton, they saw an unexpected ‘bump’ in the data above a relatively smooth background. They interpreted the bump as a particle with a mass of 145 GeV that decayed into two jets.
    But now, researchers at the Tevatron’s DZero experiment say they see no sign of CDF’s signal.

    Denisov thinks the discrepancy could come from differences in the way each experiment detects jets, or in the way they simulate the standard model. The researchers can’t compare their results to the standard model directly, he explained — they have to use so-called generators that approximate the standard model.

    “What we really see is disagreement between the generators,” he said. “It might be that something is not perfect in the CDF modeling here.” The DZero results were released online today (PDF) and were submitted to Physical Review Letters.

    CDF and DZero have only disagreed a handful of times over the past 10 years, Denisov said. In more than 500 joint papers, he could think of only two or three significant disagreements. The two teams plan to form a joint task force to figure out exactly what went wrong with the 145 GeV bump.


    Sadly the D0 experiment sees no bump in boson+dijet at Fermilab, dismissing the 4.1 sigma result of CDF.

    It is not a sure conclusion that D0 is right but it seems more likely that someone would see an effect that isn’t there by mistake than that someone would fail to see an effect that is there. This gives D0 a strong psychological advantage.
    The differences are too subtle to see from just the visual image, and it does not help that they used different bins. There does appear to be significant differences in the backgrounds while the data look quite similar. If that is the case then the problem is purely theoretical and they just need to compare their background calculations. However, the detectors are different so perhaps the backgrounds should not look exactly the same. Only the people directly involved have enough details to get to the bottom of it.



  9. http://www.science20.com/quantum_diaries_survivor/blog/plot_week_atlas_dilepton_resonance_search-80113

  10. About the problems with New Physics. It's a mess. From 2005.

  11. http://www.science20.com/quantum_diaries_survivor/plot_week_susy_higgs_150_gev bottom quarks



  12. http://online.kitp.ucsb.edu/online/lhc11/nelson/

    We don't trust SM because it gives only more questions.

    Hadrons interesting.

    p.20 NP?
    hidden valleys / displaced jets
    dark photons, lepton jets
    black holes, unusual events
    stable massive particles, bizarre tracks, cal clusters

    Those things require a different level of creativity

  13. http://online.kitp.ucsb.edu/online/lhc11/kilic/

    W+jets 80% of the background, with a missing mass.
    -mismodelling of background?
    -systematic uncertainties? energyscales (JES) changed.
    -variations? Excess still there? Proposed explanations cannot explain within SM.
    ww+wZ interesting,c 4,5% of background, about 90 GeV (little Higgs?) (bad MonteCarlo simulations?)

    NP: S vs. T-channel; T requires broken isospin, handedness top-down (with Feynman diagrams).
    S-channel, fits into background, but there is something in about 270 GeV?

    Some predictions:
    pair produces lighter resonance (4j) with two resonances
    or heavier resonances,2W+4j
    charge asymmetry

    What creates (in the analysis) the peak? delta Rjj?