Xerxes Tata

Honolulu University, Honolulu, Hawaii, United States

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Publications (156)381.26 Total impact

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    ABSTRACT: LHC searches for supersymmetry currently focus on strongly produced sparticles, which are copiously produced if gluinos and squarks have masses of a few hundred GeV. However, in supersymmetric models with heavy scalars, as favored by the decoupling solution to the SUSY flavor and CP problems, and m_{\tg}> 500 GeV as indicated by recent LHC results, chargino--neutralino (\tw_1^\pm\tz_2) production is the dominant cross section for m_{\tw_1} \sim m_{\tz_2} < m_{\tg}/3 at LHC with \sqrt{s}=7 TeV (LHC7). Furthermore, if m_{\tz_1}+m_Z \lesssim m_{\tz_2}\lesssim m_{\tz_1}+m_h, then \tz_2 dominantly decays via \tz_2\to\tz_1 Z, while \tw_1 decays via \tw_1\to \tz_1 W. We investigate the LHC7 reach in the WZ + MET channel (for both leptonic and hadronic decays of the W boson) in models with and without the assumption of gaugino mass universality. In the case of the mSUGRA/CMSSM model with heavy squark masses, the LHC7 discovery reach in the WZ+MET channel becomes competetive with the reach in the canonical MET + jets channel for integrated luminosities \sim 30 fb^-1. We also present the LHC7 reach for a simplified model with arbitrary m_{\tz_1} and m_{\tw_1} \sim m_{\tz_2}. Here, we find a reach of up to m_{\tw_1}\sim 200 (250) GeV for 10 (30) fb^-1.
    Journal of High Energy Physics 01/2012; 2012(3). · 5.62 Impact Factor
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    ABSTRACT: It is shown that, for a wide range of parameters, the dominant decays of gluinos with mass ≳500 GeV contain gauge bosons, W± and Z, among their decay products. The pair production of heavy gluinos at the SSC is thus characterized by events with 3–4 hard jets and pairs of gauge bosons. The cleanest signature comes from the case where both gluinos decay into Z followed by which leads to ~50–100 4-lepton + multijet events annually at the SSC. In addition, 1600 trilepton + multijet and about 6000 dilepton + multijet events may be expected from WZ and WW sources. The backgrounds to these signals are estimated to be small.
    International Journal of Modern Physics A 01/2012; 02(04). · 1.13 Impact Factor
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    ABSTRACT: In SUSY models with heavy squarks and gaugino mass unification, the gaugino pair production reaction pp-> \tw_1^\pm\tz_2 dominates gluino pair production for m_{\tg}\agt 1 TeV at LHC with \sqrt{s}=14 TeV (LHC14). For this mass range, the two-body decays \tw_1\to W\tz_1 and \tz_2\to h\tz_1 are expected to dominate the chargino and neutralino branching fractions. By searching for \ell b\bar{b}+MET events from \tw_1^\pm\tz_2 production, we show that LHC14 with 100 fb^{-1} of integrated luminosity becomes sensitive to chargino masses in the range m_{\tw_1}\sim 450-550 GeV corresponding to m_{\tg}\sim 1.5-2 TeV in models with gaugino mass unification. For 10^3 fb^{-1}, LHC14 is sensitive to the Wh channel for m_{\tw_1}\sim 300-800 GeV, corresponding to m_{\tg}\sim 1-2.8 TeV, which is comparable to the reach for gluino pair production followed by cascade decays. The Wh+MET search channel opens up a new complementary avenue for SUSY searches at LHC, and serves to point to SUSY as the origin of any new physics discovered via multijet and multilepton + MET channels.
    Physical review D: Particles and fields 01/2012; 85(5).
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    ABSTRACT: We propose a new way to determine the squark mass based on the shape of di-jet invariant mass distribution of supersymmetry (SUSY) di-jet events at the Large Hadron Collider (LHC). Our algorithm, which is based on event kinematics, requires that the branching ratio $B(\tilde{q} \rightarrow q \tilde{z}_1)$ is substantial for at least some types of squarks, and that $m_{\tilde{z}_1}^2/m_{\tilde{q}}^2 \ll 1$. We select di-jet events with no isolated leptons, and impose cuts on the total jet transverse energy, $E_T^{tot}=E_T(j_1)+E_T(j_2)$, on $\alpha = E_T(j_2)/m_{jj}$, and on the azimuthal angle between the two jets to reduce SM backgrounds. The shape of the resulting di-jet mass distribution depends sensitively on the squark mass, especially if the integrated luminosity is sufficient to allow a hard enough cut on $E_T^{tot}$ and yet leave a large enough signal to obtain the $m_{jj}$ distribution. We simulate the signal and Standard Model (SM) backgrounds for 100 fb$^{-1}$ integrated luminosity at 14 TeV requiring $E_T^{tot}> 700$ GeV. We show that it should be possible to extract $m_{\tilde{q}}$ to within about 3% at 95% CL --- similar to the precision obtained using $m_{T2}$ --- from the di-jet mass distribution if $m_{\tilde{q}} \sim 650$ GeV, or to within $\sim 5$% if $m_{\tilde{q}}\sim 1$ TeV.
    Physical review D: Particles and fields 02/2011; 83(9).
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    ABSTRACT: We investigate the phenomenology of Effective Supersymmetry (ESUSY) models wherein electroweak gauginos and third generation scalars have masses up to about 1~TeV while first and second generation scalars lie in the multi-TeV range. Such models ameliorate the SUSY flavor and CP problems via a decoupling solution, while at the same time maintaining naturalness. In our analysis, we assume independent GUT scale mass parameters for third and first/second generation scalars and for the Higgs scalars, in addition to m_{1/2}, \tan\beta and A_0, and require radiative electroweak symmetry breaking as usual. We analyse the parameter space which is consistent with current constraints, by means of a Markov Chain Monte Carlo scan. The lightest MSSM particle (LMP) is mostly, but not always the lightest neutralino, and moreover, the thermal relic density of the neutralino LMP is frequently very large. These models may phenomenologically be perfectly viable if the LMP before nucleosynthesis decays into the axino plus SM particles. Dark matter is then an axion/axino mixture. At the LHC, the most important production mechanisms are gluino production (for m_{1/2} ~<700~GeV) and third generation squark production, while SUSY events rich in b-jets are the hallmark of the ESUSY scenario. We present a set of ESUSY benchmark points with characteristic features and discuss their LHC phenomenology. Comment: 26 pages including 13 figures
    Journal of High Energy Physics 07/2010; · 5.62 Impact Factor
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    ABSTRACT: We examine the capability of the CERN Large Hadron Collider to discovery supersymmetry (SUSY) with energy sqrt {s} = 7{text{TeV}} and integrated luminosity of about 1 fb-1. Our results are presented within the paradigm minimal supergravity model (mSUGRA or CMSSM). Using a 6-dimensional grid of cuts for optimization of signal to background --- including missing E T --- we find for {m_{tilde{g}}} ˜ {m_{tilde{q}}} an LHC reach of {m_{tilde{g}}} 800, 950, 1100 and 1200 GeV for 0.1, 0.3, 1 and 2 fb-1, respectively. For {m_{tilde{g}}} &Lt; {m_{tilde{q}}} , the reach is instead near {m_{tilde{g}}} 480, 540, 620 and 700 GeV, for the same integrated luminosities. We also examine the LHC reach in the case of very low integrated luminosity where missing E T may not be viable. We focus on the multi-muon, multi-lepton (including electrons) and dijet signals. Although the LHC reach without E T miss is considerably lower in these cases, it is still substantial: for 0.3 fb-1, the dijet reach in terms of gluino mass is up to 600 GeV for very low m 0, while the dilepton reach is to gluino masses of ˜500 GeV over a range of m 0 values.
    Journal of High Energy Physics 04/2010; 6(6). · 5.62 Impact Factor
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    ABSTRACT: The Large Hadron Collider presents an unprecedented opportunity to probe the realm of new physics in the TeV region and shed light on some of the core unresolved issues of particle physics. These include the nature of electroweak symmetry breaking, the origin of mass, the possible constituent of cold dark matter, new sources of CP violation needed to explain the baryon excess in the universe, the possible existence of extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy problem – is it supersymmetry or extra dimensions. Many models of new physics beyond the standard model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top factory and accurate measurements of the properties of the top and its rare decays will provide a window to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the hypothesis of TeV scale strings and D brane models. An overview of these possibilities is presented in the spirit that it will serve as a companion to the Technical Design Reports (TDRs) by the particle detector groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these ideas stands the test of the LHC data will govern the course of particle physics in the subsequent decades.
    Nuclear Physics B - Proceedings Supplements. 01/2010;
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    ABSTRACT: We examine the capability of the CERN Large Hadron Collider to discovery supersymmetry (SUSY) with energy and integrated luminosity of about 1 fb−1. Our results are presented within the paradigm minimal supergravity model (mSUGRA or CMSSM). Using a 6-dimensional grid of cuts for optimization of signal to background — including missing E T — we find for an LHC reach of ~ 800, 950, 1100 and 1200 GeV for 0.1, 0.3, 1 and 2 fb−1, respectively. For , the reach is instead near ~ 480, 540, 620 and 700 GeV, for the same integrated luminosities. We also examine the LHC reach in the case of very low integrated luminosity where missing E T may not be viable. We focus on the multi-muon, multi-lepton (including electrons) and dijet signals. Although the LHC reach without E T miss is considerably lower in these cases, it is still substantial: for 0.3 fb−1, the dijet reach in terms of gluino mass is up to 600 GeV for very low m 0, while the dilepton reach is to gluino masses of ∼500 GeV over a range of m 0 values.
    Journal of High Energy Physics - J HIGH ENERGY PHYS. 01/2010; 2010(6):1-19.
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    Howard Baer, Eun-Kyung Park, Xerxes Tata
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    ABSTRACT: We present an overview of supersymmetry searches, both at collider experiments and via searches for dark matter (DM). We focus on three DM possibilities in the SUSY context: the thermally produced neutralino, a mixture of axion and axino, and the gravitino, and compare and contrast signals that may be expected at colliders, in direct detection (DD) experiments searching of DM relics left over from the Big Bang, and indirect detection (ID) experiments designed to detect the products of DM annihilations within the solar interior or galactic halo. Detection of DM particles using multiple strategies provides complementary information that may shed light on the new physics associated with the dark matter sector. In contrast to the mSUGRA model where the measured cold DM relic density restricts us to special regions mostly on the edge of the m_0-m_{1/2} plane, the entire parameter plane becomes allowed if the universality assumption is relaxed in models with just one additional parameter. Then, thermally produced neutralinos with a well-tempered mix of wino, bino and higgsino components, or with a mass adjusted so that their annihilation in the early universe is Higgs-resonance-enhanced, can be the DM. Well-tempered neutralinos typically yield heightened rates for DD and ID experiments compared to generic predictions from minimal supergravity. If instead DM consists of axinos (possibly together with axions) or gravitinos, then there exists the possibility of detection of quasi-stable next-to-lightest SUSY particles at colliding beam experiments, with especially striking consequences if the NLSP is charged, but no DD or ID detection. The exception for mixed axion/axino DM is that DD of axions may be possible. Comment: 28 pages, 11 eps figures; invited contribution to NJP Focus Issue on "Dark Matter and Particle Physics"
    New Journal of Physics 03/2009; · 4.06 Impact Factor
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    ABSTRACT: We examine the supersymmetry (SUSY) reach of the CERN LHC operating at s1/2 = 10 and 14 TeV within the framework of the minimal supergravity model (mSUGRA). We improve upon previous reach projections by incorporating updated background calculations including a variety of 2 --> n Standard Model (SM) processes. We show that SUSY discovery is possible even before the detectors are understood well enough to utilize either ETmiss or electrons in the signal. We evaluate the early SUSY reach of the LHC at s1/2 = 10 TeV by examining multi-muon plus >= 4 jets, and also lepton-free, acollinear dijet events with no missing ET cuts, and show that the greatest reach in terms of m1/2 occurs in the dijet channel, where it may be possible to probe mbar q ~ mbar g lesssim 1 TeV with just 1 fb-1 of integrated luminosity. The reach in multi-muons is slightly smaller in m1/2, but extends to higher values of m0. We find that an observable multi-muon signal will first appear in the opposite-sign dimuon channel, but as the integrated luminosity increases the relatively background-free but rate-limited same-sign dimuon, and ultimately the trimuon channel yield the highest reach. The optimized reach in these channels extends to mbar g lesssim 600 (800) GeV for an integrated luminosity of 100 pb-1 (1 fb-1). We show characteristic distributions in these channels that serve to distinguish the signal from the SM background, and also help to corroborate its SUSY origin. We then evaluate the LHC reach in various no-lepton and multi-lepton plus jets channels including missing ET cuts for s1/2 = 10 and 14 TeV, and plot the reach for integrated luminosities ranging up to 3000 fb-1 at the SLHC. For s1/2 = 10 TeV, the LHC reach extends to mbar g = 1.9, 2.3, 2.8 and 2.9 TeV for mbar q ~ mbar g and integrated luminosities of 10, 100, 1000 and 3000 fb-1, respectively. For s1/2 = 14 TeV, the LHC reach for the same integrated luminosities is to mbar g = 2.4, 3.1, 3.7 and 4.0 TeV, respectively. The reach estimates for ab-1 luminosities may be over-optimistic due to low statistics of background with very hard cuts.
    Journal of High Energy Physics 01/2009; 9(09):063-063. · 5.62 Impact Factor
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    R. S. Hundi, Sandip Pakvasa, Xerxes Tata
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    ABSTRACT: We present a locally supersymmetric extension of the minimal supersymmetric standard model (MSSM) based on the gauge group SU(3)C×SU(2)L×U(1)Y×U(1)' where, except for the supersymmetry-breaking scale which is fixed to be ˜1011GeV, we require that all non-standard-model parameters allowed by the local spacetime and gauge symmetries assume their natural values. The U(1)' symmetry, which is spontaneously broken at the intermediate scale, serves to (i) explain the weak scale magnitudes of mu and bmu terms, (ii) ensure that dimension-3 and dimension-4 baryon-number-violating superpotential operators (and, in a class of models, all DeltaB=1 operators) are forbidden, solving the proton-lifetime problem, and (iii) predict bilinear lepton-number violation in the superpotential at just the right level to accommodate the observed mass and mixing pattern of active neutrinos (leading to a novel connection between the SUSY-breaking scale and neutrino masses), while corresponding trilinear operators are strongly suppressed. The phenomenology is like that of the MSSM with bilinear R-parity violation, where the would-be lightest supersymmetric particle decays leptonically with a lifetime of ˜10-12-10-8s. Theoretical consistency of our model requires the existence of multi-TeV, stable, color-triplet, weak-isosinglet scalars or fermions, with either conventional or exotic electric charge which should be readily detectable if they are within the kinematic reach of a hadron collider. Null results of searches for heavy exotic isotopes imply that the reheating temperature of our Universe must have been below their mass scale which, in turn, suggests that sphalerons play a key role for baryogenesis. Finally, the dark matter cannot be the weakly interacting neutralino.
    Physical review D: Particles and fields 01/2009; 79(9).
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    Andrew D. Box, Xerxes Tata
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    ABSTRACT: We re-examine the one-loop renormalization group equations (RGEs) for the dimensionful parameters of the minimal supersymmetric Standard Model with broken supersymmetry, allowing for arbitrary flavour structure of the soft SUSY breaking (SSB) parameters. We include threshold effects by evaluating the $\beta$-functions in a sequence of (non-supersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We present the most general form for high scale SSB parameters that obtains if we assume that the supersymmetry breaking mechanism does not introduce new inter-generational couplings. This form, possibly amended to allow additional sources of flavour-violation, serves as a boundary condition for solving the RGEs for the dimensionful MSSM parameters. We then present illustrative examples of numerical solutions to the RGEs. We find that in a SUSY GUT with the scale of SUSY scalars split from that of gauginos and higgsinos, the gaugino mass unification condition may be violated by ${\cal O}$(10%). As another illustration, we show that in mSUGRA, the rate for the flavour-violating $\tilde{t}_1\to c\tilde{Z}_1$ decay obtained using the complete RGE solution is smaller than that obtained using the commonly-used "single-step" integration of the RGEs by a factor 10-25, and so may qualitatively change expectations for topologies from top-squark pair production at colliders. Together with the RGEs for dimensionless couplings presented in a companion paper, the RGEs in Appendix B of this paper form a complete set of one-loop MSSM RGEs that include threshold and flavour-effects necessary for two-loop accuracy.
    Physical review D: Particles and fields 10/2008; 79(3).
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    Howard Baer, Xerxes Tata
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    ABSTRACT: An abundance of astrophysical evidence indicates that the bulk of matter in the universe is made up of massive, electrically neutral particles that form the dark matter (DM). While the density of DM has been precisely measured, the identity of the DM particle (or particles) is a complete mystery. In fact, within the laws of physics as we know them (the Standard Model, or SM), none of the particles have the right properties to make up DM. Remarkably, many new physics extensions of the SM -- designed to address theoretical issues with the electroweak symmetry breaking sector -- require the introduction of new particles, some of which are excellent DM candidates. As the LHC era begins, there are high hopes that DM particles, along with their associated new matter states, will be produced in pp collisions. We discuss how LHC experiments, along with other DM searches, may serve to determine the identity of DM particles and elucidate the associated physics. Most of our discussion centers around theories with weak-scale supersymmetry, and allows for several different DM candidate particles.
    06/2008;
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    ABSTRACT: We present brief synopses of supersymmetric models where either the neutralino composition or its mass is adjusted so that thermal relic neutralinos from the Big Bang saturate the measured abundance of cold dark matter in the universe. We first review minimal supergravity (mSUGRA), and then examine its various one-parameter extensions where we relax the assumed universality of the soft supersymmetry breaking parameters. Our goal is to correlate relic-density-allowed parameter choices with expected phenomena in direct, indirect and collider dark matter search experiments. For every non-universal model, we first provide plots to facilitate the selection of ``dark-matter allowed'' parameter space points, and then present salient features of each model with respect to searches at Tevatron, LHC and ILC and also direct and indirect dark matter searches. We present benchmark scenarios that allow one to compare and contrast the non-universal models with one another and with the paradigm mSUGRA framework. We show that many implications about sparticle properties and collider signals drawn from the analysis of the relic density constraint within mSUGRA do not carry over to simple one-parameter extensions of the mSUGRA framework. We find that in many relic-density-consistent models, there is one (or more) detectable edge in the invariant mass distribution of same-flavour, opposite sign dileptons in SUSY cascade decay events at the LHC. Finally, we scan the parameter space of these various models, requiring consistency with the LEP2 constraint on the chargino mass, and with the observed relic density, and examine prospects for direct and indirect dark matter detection. We find that in a large number of cases the mechanism that causes the early universe neutralino annihilation rate to be large (so as to produce the measured relic density) also enhances the direct detection rate, and often also the rates for indirect detection of neutralino dark matter.
    Journal of High Energy Physics 03/2008; · 5.62 Impact Factor
  • Andrew D. Box, Xerxes Tata
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    ABSTRACT: In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We reexamine the renormalization group equations (RGEs) for these couplings in the minimal supersymmetric standard model (MSSM). To include threshold effects, we calculate the functions using a sequence of (nonsupersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We find that the difference between the SM couplings and their SUSY cousins that is ignored in the literature may be larger than two-loop effects which are included, and further that renormalization group evolution induces a nontrivial flavor structure in gaugino interactions. We present here the coupled set of RGEs for these dimensionless gauge and Yukawa-type couplings. The RGEs for the dimensionful soft-supersymmetry-breaking parameters of the MSSM will be presented in a companion paper.
    Physical review D: Particles and fields 03/2008; 77(5):055007-055007.
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    ABSTRACT: The branching fraction for the decays of gluinos to third generation quarks is expected to be enhanced in classes of supersymmetric models where either third generation squarks are lighter than other squarks, or in mixed-higgsino dark matter models constructed so as to be in concordance with the measured density of cold dark matter. In such scenarios, gluino production events at the CERN Large Hadron Collider should be rich in top and bottom quark jets. Requiring b jets in addition to E T miss should, therefore, enhance the supersymmetry signal relative to Standard Model backgrounds from V+jet, VV and QCD backgrounds (V=W,Z). We quantify the increase in the supersymmetry reach of the LHC from b-tagging in a variety of well-motivated models of supersymmetry. We also explore “top tagging” at the LHC. We find that while the efficiency for this turns out to be too low to give an increase in reach beyond that obtained via b-tagging, top tagging can indeed provide a confirmatory signal if gluinos are not too heavy. We also examine c jet tagging but find that it is not useful at the LHC. Finally, we explore the prospects for detecting the direct production of third generation squarks in models with an inverted squark mass hierarchy. This is signaled by b jets+ E T miss events being harder than in the Standard Model, but softer than those from the production of gluinos and heavier squarks. We find that while these events can be readily separated from the SM background (for third generation squark masses ∼300–500GeV), the contamination from the much heavier gluinos and squarks remains formidable if these are also accessible.
    European Physical Journal C 01/2008; 56(4):511-528. · 5.25 Impact Factor
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    Andrew D. Box, Xerxes Tata
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    ABSTRACT: In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We re-examine the renormalization group equations (RGEs) for these couplings in the Minimal Supersymmetric Standard Model (MSSM). To include threshold effects, we calculate the $\beta$-functions using a sequence of (non-supersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We find that the difference between the SM couplings and their SUSY cousins that is ignored in the literature may be larger than two-loop effects which are included, and further that renormalization group evolution induces a non-trivial flavour structure in gaugino interactions. We present here the coupled set of RGEs for these dimensionless gauge and "Yukawa"-type couplings. The RGEs for the dimensionful SSB parameters of the MSSM will be presented in a companion paper.
    Physical review D: Particles and fields 12/2007;
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    ABSTRACT: We observe that in SUSY models with non-universal GUT scale gaugino mass parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified value results in a smaller value of -m_{H_u}^2 at the weak scale. By the electroweak symmetry breaking conditions, this implies a reduced value of \mu^2 {\it vis \`a vis} models with gaugino mass unification. The lightest neutralino can then be mixed Higgsino dark matter with a relic density in agreement with the measured abundance of cold dark matter (DM). We explore the phenomenology of this high |M_2| DM model. The spectrum is characterized by a very large wino mass and a concomitantly large splitting between left- and right- sfermion masses. In addition, the lighter chargino and three light neutralinos are relatively light with substantial higgsino components. The higgsino content of the LSP implies large rates for direct detection of neutralino dark matter, and enhanced rates for its indirect detection relative to mSUGRA. We find that experiments at the LHC should be able to discover SUSY over the portion of parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark mass, while a 1 TeV electron-positron collider has a reach comparable to that of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt events at the LHC will likely show more than one mass edge, while its shape should provide indirect evidence for the large higgsino content of the decaying neutralinos.
    Journal of High Energy Physics 09/2007; · 5.62 Impact Factor
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    ABSTRACT: Martin has proposed a scenario dubbed ``compressed supersymmetry'' (SUSY) where the MSSM is the effective field theory between energy scales M_{\rm weak} and M_{\rm GUT}, but with the GUT scale SU(3) gaugino mass M_3<< M_1 or M_2. As a result, squark and gluino masses are suppressed relative to slepton, chargino and neutralino masses, leading to a compressed sparticle mass spectrum, and where the dark matter relic density in the early universe may be dominantly governed by neutralino annihilation into ttbar pairs via exchange of a light top squark. We explore the dark matter and collider signals expected from compressed SUSY for two distinct model lines with differing assumptions about GUT scale gaugino mass parameters. For dark matter signals, the compressed squark spectrum leads to an enhancement in direct detection rates compared to models with unified gaugino masses. Meanwhile, neutralino halo annihilation rates to gamma rays and anti-matter are also enhanced relative to related scenarios with unified gaugino masses but, depending on the halo dark matter distribution, may yet be below the sensitivity of indirect searches underway. In the case of collider signals, we compare the rates for the potentially dominant decay modes of the stop_1 which may be expected to be produced in cascade decay chains at the LHC: \tst_1\to c\tz_1 and \tst_1\to bW\tz_1. We examine the extent to which multilepton signal rates are reduced when the two-body decay mode dominates. For the model lines that we examine here, the multi-lepton signals, though reduced, still remain observable at the LHC. Comment: 22 pages including 24 eps figures
    Journal of High Energy Physics 07/2007; · 5.62 Impact Factor
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    ABSTRACT: We analyze the potential of the CERN Large Hadron Collider on the reach of the focus point (FP) region in the mSUGRA parameter space. This region, consistent with WMAP results, is characterized by multi-TeV masses for the superpartners of quarks and leptons and relatively light charginos and neutralinos. Moreover, since the LSP has a substantial higgsino component, it is expected that the gluino decays predominantly to third generation quarks, producing a final state with multiple hard b jets. Analyzing events with $\not\!\!{E_T}+n$ t+ n jets + tagged b-jets, we show that the LHC reach can improve as much as 20% from current projections. Although we performed the analysis specifically for the FP region, the b-tagging should be important to enhance the SUSY signal in a variety of models where a relatively light gluino decays mostly to third generation quarks.
    Brazilian Journal of Physics 06/2007; · 0.60 Impact Factor

Publication Stats

4k Citations
381.26 Total Impact Points

Institutions

  • 1995–2014
    • Honolulu University
      Honolulu, Hawaii, United States
  • 1985–2014
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 2012
    • University of Oklahoma
      Norman, Oklahoma, United States
  • 1987–2010
    • University of Wisconsin–Madison
      • Department of Physics
      Madison, Wisconsin, United States
  • 1990–2009
    • University of Hawaiʻi at Mānoa
      • Department of Physics and Astronomy
      Honolulu, HI, United States
  • 2008
    • University of Hawaiʻi at Hilo
      Hilo, Hawaii, United States
    • Hawaii Pacific University
      Honolulu, Hawaii, United States
  • 1993–2006
    • Florida State University
      • Department of Physics
      Tallahassee, FL, United States
  • 1989
    • Illinois Institute of Technology
      Chicago, Illinois, United States
  • 1979–1985
    • University of Texas at Austin
      • Department of Physics
      Austin, Texas, United States
  • 1984
    • Michigan State University
      • Department of Physics and Astronomy
      East Lansing, MI, United States