arXiv subjects

S. Mrenna

Publications and source records attributed to S. Mrenna.

45 records · Page 3Linked to original sources

arXiv1996

Low energy supersymmetry with a neutralino LSP and the CDF eeγγ+ missing E_T event

We present a refined and expanded analysis of the CDF $eeγγ+ \Et$ event as superpartner production, assuming the lightest neutralino is the lightest supersymmetric particle. A general low-energy Lagrangian is constrained by a minimum cross section times branching ratio into two electrons and two photons, kinematics consistent with the event, and LEP1-LEP130 data. We examine how the supersymmetric parameters depend on the kinematics, branching ratios and experimental predictions with a selectron interpretation of the event, and discuss to what extent these are modified by other interpretations. Predictions for imminent CERN LEP upgrades and the present and future Fermilab Tevatron are presented. Finally, we briefly discuss the possible connection to other phenomena including a light stop, the neutralino relic density, the shift in $R_b$ and the associated shift in $α_s$, and implications for the form of the theory.

hep-ph↗

arXiv1996

Signals of Dynamical Supersymmetry Breaking in a Hidden Sector

If supersymmetry is dynamically broken in a hidden sector, the gauginos typically have unacceptably small masses. This situation can be corrected if a non-Abelian gauge interaction becomes strong at a scale of order 1 TeV and induces dynamical gaugino masses. We discuss the typical signals of this scenario at present and future colliders.

hep-ph↗

arXiv1996

Search for supersymmetry with a light gravitino at the Fermilab Tevatron and CERN LEP colliders

We analyze the prospects for discovering supersymmetry at the Fermilab Tevatron and CERN LEP colliders in the scenario that the lightest supersymmetric particle is a gravitino of mass < 1 keV. We consider in particular the case that the lightest neutralino has a nearly 100% branching fraction into gravitino + photon within the detector. This implies that supersymmetric events should contain both missing (transverse) energy and two energetic photons. Therefore one can search for supersymmetry simply through inclusive production of superpartners. We consider the exclusion and reach capabilities of the Tevatron in exploring the supersymmetric parameter space, and study the efficiencies which can be achieved in this search. We also consider the discovery reach and backgrounds at LEP with $\sqrt{s} =$ 160, 175, and 190 GeV.

hep-ph↗

arXiv1996

SPYTHIA, A Supersymmetric Extension of PYTHIA 5.7

SPYTHIA is an event level Monte Carlo program which simulates particle production and decay at lepton and hadron colliders in the Minimal Supersymmetric Standard Model (MSSM). It is an extension of PYTHIA 5.7, with all of its previous capabilities. This paper is meant to supplement the PYTHIA/JETSET user manual, providing a description of the new particle spectrum, hard scattering processes, and decay modes. Several examples of using the program are provided.

hep-ph↗

arXiv1996

Effects of QCD Resummation on Distributions of Top--Antitop Quark Pairs Produced at the Tevatron

We study the kinematic distributions of top--antitop quark pairs produced at the Tevatron, including the effects of initial state and final state multiple soft gluon emission, using the Collins--Soper--Sterman resummation formalism. The resummed results are compared with those predicted by the showering event generator PYTHIA for various distributions involving the top--antitop quark pair and the individual top quark or antiquark. The comparison between the experimental and predicted distributions will be a strong test of our understanding and application of perturbative QCD. Our results indicate that the showering event generators do not produce enough radiation. We reweight the PYTHIA distributions to agree with our resummed calculation, then use the reweighted events to better estimate the true hadronic activity in top--antitop quark pair production at hadron colliders.

hep-ph↗

arXiv1996

Do About Half the Top Quarks at FNAL Come From Gluino Decays?

We argue that it is possible to make a consistent picture of FNAL data including the production and decay of gluinos and squarks. The additional cross section is several pb, about the size of that for Standard Model (SM) top quark pair production. If the stop squark mass is small enough, about half of the top quarks decay to stop squarks, and the loss of SM top quark pair production rate is compensated by the supersymmetric processes. This behavior is consistent with the reported top quark decay rates in various modes and other aspects of the data, and suggests several other possible decay signatures. This picture can be tested easily with more data, perhaps even with the data in hand, and demonstrates the potential power of a hadron collider to determine supersymmetric parameters. It also has implications for the top mass measurement and the interpretation of the LEP $R_b$ excess.

hep-ph↗

arXiv1996

Supersymmetric analysis and predictions based on the CDF eeγγ+ missing E_T event

We have analyzed the single $\eegg + \slashchar{E}_T$ event at CDF and found that the expected rate and kinematics are consistent with selectron pair production. We consider two classes of general low-energy supersymmetric theories, where either the lightest neutralino (``neutralino LSP'' scenario) or the gravitino (``light gravitino'' scenario) is the lightest supersymmetric particle. The parameter space of the supersymmetric Lagrangian is tightly constrained by the kinematics of the event and the branching ratios for the necessary decay chain of the selectron. We identify a region of the parameter space satisfying all low-energy constraints, and consistent with the selectron interpretation of the $eeγγ+ \Et$ event. We discuss other supersymmetric processes at Fermilab Tevatron and at CERN LEP in both scenarios that could confirm or exclude a supersymmetric explanation of the event, and that could distinguish between the neutralino LSP and the light gravitino scenarios.

hep-ph↗

arXiv1995

Detecting a Light Stop from Top Decays at the Tevatron

We study the possibility of discovering or excluding a light top squark (stop) based on top quark decays in the t-tbar events produced at the Fermilab Tevatron. In particular, we consider the Minimal Supersymmetric Standard Model with the sparticle spectrum m_{chi^+_1}+m_b, M_W+m_{chi^0_1}+m_b > m_{stop} > m_{chi^0_1}+m_c, where chi^0_1 is the lightest neutralino and chi^+_1 is the lightest chargino, so that t -> stop chi^0_1 and stop -> c chi^0_1. All other sparticle masses are assumed to be heavier than m_t. Such a spectrum seeks to explain the experimental values of alpha_s(M_Z^2), R_b and A_{LR} obtained from LEP/SLC data. We find that the prospect to observe a light stop via this channel at the Tevatron is very promising.

hep-ph↗

arXiv1995

High-p_T Higgs Boson Production at Hadron Colliders to Order(alpha_s G_Fermi^3)

We study high--$p_T$ Higgs boson production at hadron colliders to order($α_s$ $G_F^3$) in hadron collisions. In particular, we investigate the process $g+q/\bar{q}\ra q/\bar{q}+H$, where $q=u,d,c,s,$ or $b$, for the LHC (a $\sqrt{s}=$14~TeV, proton--proton collider). Our results are compared to the order($α_s^3$ $G_F$) calculation. The associated production of a high--$p_T$ Higgs boson with a $b$--quark or anti--quark is comparable to the order($α_s^3$ $G_F$) calculation because of the large top quark mass and the additional contribution of electroweak gauge and Goldstone bosons. The associated production of light quarks, however, is not significant. We also comment on new physics effects in the framework of the electroweak chiral Lagrangian.

hep-ph↗