arXiv subjects

Xerxes Tata

Publications and source records attributed to Xerxes Tata.

115 records · Page 7Linked to original sources

arXiv1995

Prospects for Supersymmetry at LEP2

Working within the framework of the minimal supergravity model with gauge coupling unification and radiative electroweak symmetry breaking (SUGRA), we map out regions of parameter space explorable by experiments at LEP2, for center of mass energy options of $\sqrt{s}=150,\ 175$, $190$ and 205 GeV. We compute signals from all accessible $2 \rightarrow 2$ SUSY pair production processes using the ISAJET simulation program, and devise cuts that enhance the signal relative to Standard Model backgrounds, and which also serve to differentiate various supersymmetric processes from one another. We delineate regions of SUGRA parameter space where production of neutralino pairs, chargino pairs, slepton pairs and the production of the light Higgs scalar of SUSY is detectable above Standard Model backgrounds and distinguishable from other SUSY processes. In addition, we find small regions of SUGRA parameter space where $\te\te$, $\tz_2\tz_2$ and $\tnu_L\tnu_L$ production yields spectacular events with up to four isolated leptons. The combined regions of parameter space explorable by LEP2 are compared with the reach of Tevatron Main Injector era experiments. Finally, we comment on how the reach via the neutralino pair channel is altered when the radiative electroweak symmetry breaking constraint is relaxed.

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arXiv1995

SUPERSYMMETRY REACH OF AN UPGRADED TEVATRON COLLIDER

We examine the capability of a $\sqrt{s}=2$ TeV Tevatron $p\bar p$ collider to discover supersymmetry, given a luminosity upgrade to amass $25\ fb^{-1}$ of data. We compare with the corresponding reach of the Tevatron Main Injector ($1\ fb^{-1}$ of data). Working within the framework of minimal supergravity with gauge coupling unification and radiative electroweak symmetry breaking, we first calculate the regions of parameter space accessible via the clean trilepton signal from $\tw_1\tz_2\to 3\ell +\eslt$ production, with detailed event generation of both signal and major physics backgrounds. The trilepton signal can allow equivalent gluino masses of up to $m_{\tg}\sim 600-700$ GeV to be probed if $m_0$ is small. If $m_0$ is large, then $m_{\tg}\sim 500$ GeV can be probed for $μ<0$; however, for $μ>0$ and large values of $m_0$, the rate for $\tz_2\to\tz_1\ell\bar{\ell}$ is suppressed by interference effects, and there is {\it no} reach in this channel. We also examine regions where the signal from $\tw_1\overline{\tw_1}\to \ell\bar{\ell}+\eslt$ is detectable. Although this signal is background limited, it is observable in some regions where the clean trilepton signal is too small. Finally, the signal $\tw_1\tz_2\to jets+\ell\bar{\ell} +\eslt$ can confirm the clean trilepton signal in a substantial subset of the parameter space where the trilepton signal can be seen. We note that although the clean trilepton signal may allow Tevatron experiments to identify signals in regions of parameter space beyond the reach of LEP II, the dilepton channels generally probe much the same region as LEP II.

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arXiv1995

Recent Developments in supersymmetry Search Strategies

After a quick review of the framework for phenomenological analyses of supersymmetry, we summarize current limits on supersymmetric particle masses and discuss strategies for their searches at the Fermilab Tevatron and the LHC. We also discuss the sense in which such searches as well as those that may be carried out at LEP complement one another. Finally, we touch upon the prospects for more ambitious measurements such as those of sparticle masses and couplings. Such measurements could (a) help pin down model parameters, (b) perhaps, serve to test our ideas of physics at very high energy, and (c) provide the most direct test of supersymmetry.

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arXiv1994

Looking Beyond the Standard Model

Within the framework of the Standard Model, the scale of electroweak symmetry breaking is unstable to radiative corrections. We discuss two broad classes of models of new physics (one with a strongly interacting and the other with a perturbatively coupled electroweak symmetry breaking sector) in which this stability is restored. After reviewing experimental constraints on these, we discuss the implications of these types of models for experiments, both at currently operating colliders as well as the next generation of colliders under consideration for construction. Other extensions of the Standard Model are briefly alluded to.

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arXiv1994

Searching for Supersymmetry: A Minireview

After a lightning review of current bounds on the masses of supersymmetric particles, we describe strategies that may be helpful for extracting signals from the production of squarks, gluinos or top squarks, and from associated chargino-neutralino production at the Tevatron. We then briefly review SUSY signals at hadron and $e^+e^-$ supercolliders. We discuss how various SUSY signals may be correlated within the supergravity framework and indicate the sense in which $e^+e^-$ and hadron colliders may be complementary. **Presented at the Eighth DPF Meeting, Albuquerque, NM, August, 1994**

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arXiv1993

Aspects of Chargino-Neutralino Production at the Tevatron Collider

We have used ISAJET 7.0/ISASUSY 1.0 to evaluate the rates and study distributions for trilepton events from the leptonic decays of charginos and neutralinos produced at the Fermilab Tevatron via the reaction, $p\bar p\rightarrow \tilde{W_1} \tilde{Z_2}$ + X for cuts inspired by the CDF and D0 experiments. We find that about 60\% of these events do not contain any jets, and so should be easily identifiable over Standard Model backgrounds from $t\bar{t}$ and WZ production, provided that the decay $\tilde{Z_2}\rightarrow\tilde{Z_1}Z$ is kinematically inaccessible. We further show that, with suitable cuts, these backgrounds can be reduced to less than 1-2 $fb$ even if $n_{jet} = 1$, effectively increasing the SUSY sample by 50\%. We confirm that the signal is only rate-limited, and that the Fermilab Tevatron after an accumulation of 100 $pb^{-1}$ of integrated luminosity will be able to explore parameters well beyond the range of LEP and, if sleptons are substantially lighter than squarks, close to the reach of LEP 200.

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arXiv1992

Tau Signals of R-parity breaking at LEP 200

The detectability at LEP 200 of explicit $R$-parity breaking by tau-number $(L_τ)$ violating operators is considered. The assumption of $L_τ$-violation is motivated by the relative lack of constraints on such couplings but similar considerations apply to explicit $L_e$- or $L_μ$-violation. The $LSP$, now unstable, and not necessarily neutral, decays via $L_τ$-violating modes. Only signals from the production and decays of $LSP$ pairs are considered, thereby avoiding any dependence on the sparticle mass spectrum. Rather spectacular signals are predicted: spherical events with $m$ leptons (usually containing at least one $τ$) and $n$ jets $(m,n \leq 4)$, the most characteristic of which are like-sign $ττ$ events. These signals are enumerated for each $LSP$ candidate and quantitative estimates are provided for the favoured case when the $LSP$ is a neutralino. Other new physics signals, which can mimic these signatures, are also briefly discussed.

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