arXiv subjects

Glennys R. Farrar

Publications and source records attributed to Glennys R. Farrar.

At least 127 records · Page 7Linked to original sources

arXiv1997

Experimental and Cosmological Implications of Light Gauginos

Gauginos may be nearly massless at tree level, with loop corrections giving a gluino mass of order 100 MeV and a photino mass of order 1 GeV. Relic photinos can naturally account for the observed dark matter, but their detection is more difficult than for conventional WIMPs. The lightest gluino-containing baryon could account for the recently observed ultra-high energy cosmic rays, which violate the GZK bound. The predicted mass and properties of the gluino-gluino boundstate agree with those of the eta(1410), a flavor singlet pseudoscalar meson which has proved difficult to reconcile with QCD predictions. Laboratory experiments presently exclude only a small portion of the interesting parameter space, although improvements expected in the next year may lead to complete exclusion or discovery.

hep-ph↗

arXiv1997

Status of Light Gaugino Scenarios

I summarize recent devlopments in supersymmetry scenarios which leave some or all gauginos light. The emphasis is on experimental and phenomenological progress in the past year.

hep-ph↗

arXiv1997

Are Light Gluinos Dead?

Not yet. ALEPH's recent exclusion limit employs an aggressive determination of theoretical uncertainties using a simplified application of the Bayesian method. The validity of their analysis can be evaluated by its further implications, such as contradicting the existence a b quark and requiring relations between hadronic event-shape observables which are not observed. Traditional error estimation methods result in a much larger estimate for the theoretical uncertainties. This puts the ALEPH and also Csikor-Fodor limits at the $\sim 1~ σ$ level for the very light gluino scenario. A recent astrophysical result implies direct searches will be more difficult than previously anticipated, adding to the importance of reducing the QCD uncertainty in predictions sensitive to indirect effects of light gluinos. Some possible indications in favor of a light gluino are noted.

hep-ph↗

arXiv1997

Dark Matter and Cosmic Rays from Light Gauginos

An attractive class of SUSY-breaking mechanisms predicts a photino mass of order 1 GeV. Relic photinos can naturally account for the observed dark matter. Detection of these light photinos is discussed and contrasted with conventional WIMPs. In this scenario the gluino mass is about 100 MeV. The lightest gluino-containing baryon could account for the recently observed ultra-high energy cosmic rays, which violate the GZK bound.

hep-ph↗

arXiv1997

SUSY Breaking and Light Gauginos

Several supersymmetry breaking mechanisms do not produce dimension-3 operators. I show here that this scenario is consistent with present observations and has several significant virtues: i) When there are no dimension-3 SUSY-breaking operators there is no SUSY-CP problem. ii) SUSY-breaking need not occur through gauge singlets, so that the cosmological problems often encountered in hidden sector SUSY-breaking can be avoided. iii) Photino and gluino and $R$-hadron masses are naturally consistent with relic photinos providing the required dark matter density. Requiring spontaneous electroweak symmetry implies that scalar masses are mostly in the $\sim 100$ GeV range. The gluino and photino are massless at tree level. At 1-loop, the gluino and photino masses at the ew scale are predicted to be $m_{\gluino}\sim 10 - 600$ MeV and $m_{\photino} \sim 100 - 1400$ MeV. New hadrons with mass $\sim 1 \frac{1}{2}$ GeV are predicted and described. The ``extra'' flavor singlet pseudoscalar in the $ι(1440)$ region which has been observed in several experiments is naturally interpreted as the mainly-$\gluino \gluino$ bound state which gets its mass via the QCD anomaly. Its superpartner, a gluon-gluino bound state, would be the lightest $R$-hadron. For the most interesting portions of parameter space the $R^0$ lifetime is $10^{-6} - 10^{-10}$ sec, so existing searches would not have been sensitive to it. Search strategies and other consequences of the scenario are briefly mentioned.

hep-ph↗

arXiv1997

On the relic abundance of light photinos

We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and $R^0$'s (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R^0 mass to the photino mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the $R^0 \leftrightarrow \photino ππ$ and $R^0 π\leftrightarrow \photino π$ reactions to identify cosmologically favored regions of $R^0$ lifetime as a function of $R^0$ and photino masses.

astro-ph↗

arXiv1997

Light Gluino Mass and Condensate from Properties of $η$ and $η'$

We investigate whether known properties of the $η'$ meson are consistent with its being the Goldstone boson of the spontaneously broken anomaly-free R symmetry required in the light gluino scenario. We fit the masses and $2γ$ decays of the $η$ and $η'$ mesons, and also their production in radiative $J/ψ$ decays. We find that the $η-η'$ system is well-described in the light gluino scenario, if $m_λ\simeq (84-144) MeV$ and $<{\barλ}λ> \simeq -(0.15-0.36) GeV^3$. These values are in the range expected when the gluino gets its mass entirely from radiative corrections.

hep-ph↗

arXiv1996

Determining the Gluonic Content of Isoscalar Mesons

The gluonic widths of four leading glueball candidates are determined from their production in radiative quarkonium decays, allowing quantitative estimation of their glue content. Lattice predictions for the scalar and tensor channels seem to be in reasonable agareement with present data (allowing for mixing with $q \bar{q}$ states). However there is a glueball-like-state in the pseudoscalar spectrum whose mass is considerably lower than expected from lattice estimates.

hep-ph↗

arXiv1996

Phenomenology of ``inos'' in the Light Gaugino Scenario and Possible Evidence for a $\sim 53$ GeV Chargino

The tree-level-massless gaugino scenario predicts that the lighter chargino mass is less than m_W and that gluino and lightest neutralino masses are $\lsi 1$ GeV. In this case the dominant decay mode of charginos and non-LSP neutralinos is generically to three jets. The excess of "4j" events with total invariant mass $\sim 105$ GeV observed in LEP running at 130-136 GeV is noted to be consistent with pair production of $\sim 53$ GeV charginos. Data at 161 and 172 GeV from Fall, 1996, cannot conclusively test this hypothesis (because cuts to eliminate $W^+W^-$ background reduce the efficiency significantly) but is suggestive that the signal persists.

hep-ph↗

arXiv1996

SUSY and the Electroweak Phase Transition

We analyze the effective 3 dimensional theory previously constructed for the MSSM and multi-Higgs models to determine the regions of parameter space in which the electroweak phase transition is sufficiently strong for a $B+L$ asymmetry to survive in the low temperature phase. We find that the inclusion of all supersymmetric scalars and all 1-loop corrections has the effect of enhancing the strength of the phase transition. Without a light stop or extension of the MSSM the phase transition is sufficiently first order only if the lightest Higgs mass $M_{h}\lsi 70$ GeV and $tanβ\lsi 1.75$.

hep-ph↗

arXiv1996

Determining the Gluonic Content of Isoscalar Mesons

We develop tools to determine the gluonic content of a resonance of known mass, width and $J^{PC}$ from its branching fraction in radiative quarkonium decays and production cross section in $γγ$ collisions. We test the procedures by applying them to known $q\bar{q}$ mesons, then analyze four leading glueball candidates. We identify inconsistencies in data for $J/ψ\to γf_0(1500)$ and $J/ψ\to γf_J(1710)$ whose resolution can quantify their glueball status.When $Γ(f_0(1500) \to γγ)$ and $Γ(f_J(1710) \to γγ)$ are known, the $n\bar{n}, s\bar{s},gg$ mixing angles can be determined. The enigmatic situation in 1400-1500 MeV region of the isosinglet $0^{-+}$ sector is discussed.

hep-ph↗

arXiv1996

Phenomenology of Charginos and Neutralinos in the Light Gaugino Scenario

The light gaugino scenario predicts that the lighter chargino mass is less than m_W, gluino and lightest neutralino masses are <~ 1 GeV, and the dominant decay mode of charginos and non-LSP neutralinos is generically to three jets. The excess "4j" events observed by ALEPH in e+ e- annihilation at 133 GeV may be evidence that m(C_1) = 53 GeV. If so, m(N_2) = 110-121 GeV, m(N_2) = 38-63 GeV, m(N_3) = 75-68 GeV; m(sneu_e) is probably ~m(C_1). A detailed analysis of the multi-jet events is needed to exclude this possibility. Consequences for FNAL and higher energy LEP running are given.

hep-ph↗

arXiv1996

Detecting Gluino-Containing Hadrons

When SUSY breaking produces only dimension-2 operators, gluino and photino masses are of order 1 GeV or less. The gluon-gluino bound state has mass 1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and lifetime is largely unconstrained because missing energy and beam dump techniques are ineffective. With only small modifications, upcoming K^0 decay experiments can study most of the interesting range. The lightest gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to find it and the uud-gluino are also discussed.

hep-ph↗

arXiv1996

New Signatures of Squarks

When the gluino is light and long lived, missing energy is a poor signature for both squarks and gluinos. Instead, $S_q S_q^*$ production in $e^+ e^-$ and $p \bar{p}$ collisions characteristically results in events with $\ge 4$ jets. Methods are proposed for deciding whether an observed excess of 4-jet events is due to $S_q S_q^*$ production. The recent report by ALEPH of observation of 14 4-jet events when 7 were expected is discussed.

hep-ph↗

arXiv1995

Phenomenology of Light Gauginos: I. Motivation, Masses, Lifetimes and Limits

I explore an economical variant on supersymmetric standard models which may be indicated on cosmological grounds and is shown to have no SUSY-CP problem. Demanding radiative electroweak symmetry breaking suggests that the Higgs is light; other scalar masses may be ~ 100-200 GeV or less. In this case the gluino and photino, while massless at tree level, have 1-loop masses m(gluino) ~ 100 - 600 MeV and m(photino) ~ 100 - 1000 MeV. New hadrons with mass ~ 1 - 3 GeV are predicted and their lifetimes estimated. Existing experimental limits are discussed.

hep-ph↗

arXiv1995

Phenomenology of Light Gauginos: II. Experimental Signatures

When SUSY breaking produces only dimension-2 terms in the minimal supersymmetric standard model, the parameters of the theory can be rather well constrained. This paper deals with strategies for the detection of the new hadrons predicted in the 1-3 GeV mass range. Some limits are obtained. New signatures for squarks are also given. Squark masses as small as 45 GeV are not yet excluded.

hep-ph↗

arXiv1995

LIGHT PHOTINOS AS DARK MATTER

There are good reasons to consider models of low-energy supersymmetry with very light photinos and gluinos. In a wide class of models the lightest $R$-odd, color-singlet state containing a gluino, the $\r0$, has a mass in the 1-2 GeV range and the slightly lighter photino, $\pho$, would survive as the relic $R$-odd species. For the light photino masses considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and $R^0$ are close in mass. Including $\r0\longleftrightarrow\pho$ processes, we find that the photino relic abundance is most sensitive to the $\r0$-to-$\pho$ mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an $\r0$-to-$\pho$ mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis.

astro-ph↗

arXiv1995

Phenomenology of Light Gauginos

I advocate the virtues of a very economical version of the minimal supersymmetric standard model which avoids cosmological problems often encountered in dynamical SUSY-breaking and solves the SUSY-CP problem. Imposing $m_Z=91$ GeV and $m_t \sim 175$ GeV implies that scalar masses are generally $100-200$ GeV. The gluino and photino are massless at tree level. At 1-loop, the gluino mass is predicted to be in the range $m_{\gluino}: 100 - 600$ MeV and the photino mass can be estimated to be $m_{\photino}: 100 - 1400$ MeV. New hadrons with mass $\sim 1 \frac{1}{2}$ GeV are predicted and described. The ``extra'' flavor singlet pseudoscalar observed in two experiments in the $ι(1440)$ region, if confirmed, is naturally interpreted as the state which gets its mass via the QCD anomaly. Its superpartner, a gluon-gluino bound state, generally has a lifetime longer than $5~10^{-11}$ sec and would not have shown up in existing searches. Search strategies and other consequences of the scenario are discussed.

hep-ph↗