Search for SUSY in (Leptons +) Jets + E_T^miss final states

We study the observability of the squarks and gluinos in CMS at LHC. Classical E_T^miss + jets final state as well as a number of additional multilepton signatures (0 leptons, 1 lepton, 2 leptons of the same sign, 2 leptons of the opposite sign and 3 leptons) are investigated . The detection of these sparticles relies on the observation of an excess of events over Standard Model background expectations. The study is made in the framework of a minimal SU(5) mSUGRA model as a function of m_0, m_1/2 for 4 sets of model parameters : tan(beta) = 2 or 35 and sign(mu) = +/- 1 and for fixed value of A_0 = 0. The CMS detector response is modelled using CMSJET 4.51 fast MC code (non-GEANT). The results obtained are presented as 5 sigma detection contours in the m_0, m_1/2 planes and with optimized selection cuts in various regions of the parameter space. The result of these investigations is that with integrated luminosity L=10^5 pb^-1 the squark and gluino mass reach is about 2.5 TeV and covers most of the interesting parts of parameter space according to neutralino relic density expectations. The influence of signal and background cross-section uncertainties on the reach contours is estimated. The effect of pile-up on signal and background is also discussed. This effect is found to be insignificant for E_T^miss and single lepton signatures, whilst only a minor deterioration is seen for multilepton final states.Comment: 28 pages, 28 figure

Reach of the CERN LHC for the Minimal Anomaly-Mediated SUSY Breaking Model

We examine the reach of the CERN LHC pp collider for supersymmetric models where the dominant contribution to soft SUSY breaking parameters arises from the superconformal anomaly. In the simplest viable anomaly mediated SUSY breaking (AMSB) model, tachyonic slepton squared masses are made positive by adding a universal contribution m_0^2 to all scalars. We use the event generator ISAJET to generate AMSB signal events as a function of model parameter space. Assuming an integrated luminosity of 10 fb-1, the LHC can reach to values of $m_{\tg}\sim 2.3$ TeV for low values of $m_0$, where the dilepton plus jets plus E_T(missing) channel offers the best reach. For large $m_0$, the best signature is typically 0 or 1 isolated lepton plus jets plus E_T(missing); in this case the reach is typically diminished to values of $m_{\tg}\sim 1.3$ TeV. The presence of terminating tracks in a subset of signal events could serve to verify the presence of a long lived lightest chargino which is generic in the minimal AMSB model.Comment: 11 page REVTEX file including 3 PS figure

Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses

The reach of the Fermilab Tevatron for supersymmetric matter has been calculated in the framework of the minimal supergravity model in the clean trilepton channel. Previous analyses of this channel were restricted to scalar masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point (HB/FP) region, where the superpotential \mu parameter becomes small. In this region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated luminosity, the Tevatron reach in the trilepton channel extends up to m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected and references adde

LHC Reach for Gauge Mediated Supersymmetry Breaking Models Via Prompt Photon Channels

We evaluate the supersymmetry reach of the Large Hadron Collider within the gauge-mediated low energy supersymmetry breaking framework, assuming that a neutralino is the second lightest sparticle and that it decays promptly into a gravitino which escapes detection. We find that the maximum reach is obtained via a search for inclusive \gamma\gamma+\eslt events coming dominantly from chargino and neutralino production. Assuming an integrated luminosity of 10~$fb^{-1}$, we find that LHC experiments will be able to probe values of the model parameter \Lambda \alt 400 TeV, corresponding to $m_{\tg} \leq 2.8$ TeV. A measure of the model parameter $\Lambda$ may be possible from the photon $p_T$ spectrum.Comment: 10 page Revtex file plus 4 EPS figure

Supersymmetry Reach of Tevatron Upgrades: The Large tan⁡β\tan\beta Case

The Yukawa couplings of the tau lepton and the bottom quark become comparable to, or even exceed, electroweak gauge couplings for large values of the SUSY parameter $\tan\beta$. As a result, the lightest tau slepton \ttau_1 and bottom squark \tb_1 can be significantly lighter than corresponding sleptons and squarks of the first two generations. Gluino, chargino and neutralino decays to third generation particles are significantly enhanced when $\tan\beta$ is large. This affects projections for collider experiment reach for supersymmetric particles. In this paper, we evaluate the reach of the Fermilab Tevatron $p\bar p$ collider for supersymmetric signals in the framework of the mSUGRA model. We find that the reach via signatures with multiple isolated leptons ($e$ and $\mu$) is considerably reduced. For very large $\tan\beta$, the greatest reach is attained in the multi-jet+\eslt signature. Some significant extra regions may be probed by requiring the presence of an identified $b$-jet in jets+\eslt events, or by requiring one of the identified leptons in clean trilepton events to actually be a hadronic 1 or 3 charged prong tau. In an appendix, we present formulae for chargino, neutralino and gluino three body decays which are valid at large $\tan\beta$.Comment: 31 page Revtex file including 10 PS figure

SUSY backgrounds to Standard Model calibration processes at the LHC

One of the first orders of business for LHC experiments after beam turn-on will be to calibrate the detectors using well understood Standard Model (SM) processes such as W and Z production and ttbar production. These familiar SM processes can be used to calibrate the electromagnetic and hadronic calorimeters, and also to calibrate the associated missing transverse energy signal. However, the presence of new physics may already affect the results coming from these standard benchmark processes. We show that the presence of relatively low mass supersymmetry (SUSY) particles may give rise to significant deviations from SM predictions of Z+jets and W+jets events for jet multiplicity $\ge 4$ or $\ge 5$, respectively. Furthermore, the presence of low mass SUSY may cause non-standard deviations to appear in top quark invariant and transverse mass distributions. Thus, effects that might be construed as detector mal-performance could in fact be the presence of new physics. We advocate several methods to check when new physics might be present within SM calibration data.Comment: 14 pages, 6 figures, 3 table

Implications of Compressed Supersymmetry for Collider and Dark Matter Searches

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 figure

On nodal sets for Dirac and Laplace operators

We prove that the nodal set (zero set) of a solution of a generalized Dirac equation on a Riemannian manifold has codimension 2 at least. If the underlying manifold is a surface, then the nodal set is discrete. We obtain a quick proof of the fact that the nodal set of an eigenfunction for the Laplace-Beltrami operator on a Riemannian manifold consists of a smooth hypersurface and a singular set of lower dimension. We also see that the nodal set of a $\Delta$-harmonic differential form on a closed manifold has codimension 2 at least; a fact which is not true if the manifold is not closed. Examples show that all bounds are optimal.Comment: LaTeX, uses pstricks macro-package, 15 pages with 2 figures; to appear in Commun. Math. Phy

SO(10) SUSY GUTs with mainly axion cold dark matter: implications for cosmology and colliders

Supersymmetric grand unified theories based on the gauge group SO(10) are highly motivated. In the simplest models, one expects t-b-\tau Yukawa coupling unification, in addition to gauge, matter and Higgs unification. Yukawa unification only occurs with very special GUT scale boundary conditions, leading to a spectra with ~10 TeV first and second generation scalars, TeV-scale third generation scalars, and light gauginos. The relic density of neutralino cold dark matter is calculated to be 10^2-10^4 times higher than observation. If we extend the theory with the PQWW solution to the strong CP problem, then instead a mixture of axions and axinos comprises the dark matter, with the measured abundance. Such a solution solves several cosmological problems. We predict a rather light gluino with m(gluino)~300-500 GeV that should be visible in either Tevatron or forthcoming LHC run 1 data. We would also expect ultimately a positive result from relic axion search experiments.Comment: 6 pages plus 2 .eps figures; invited talk given at Axions 2010 meeting, University of Florida, Jan. 15-17, 201