arXiv subjects

M. Bisset

Publications and source records attributed to M. Bisset.

7 recordsLinked to original sources

arXiv2011

Improving SUSY Spectrum Determinations at the LHC with Wedgebox Technique

The LHC has the potential not only to discover supersymmetry (SUSY), but also to permit fairly precise measurements of at least a portion of the sparticle spectrum. Proposed mass reconstruction methods rely upon either inverting invariant mass endpoint expressions or upon solving systems of mass-shell equations. These methodologies suffer from the weakness that one certain specific sparticle decay chain is assumed to account for all the events in the sample. Taking two examples of techniques utilizing mass-shell equations, it is found that also applying the wedgebox technique allows for the isolation of a purer event sample, thus avoiding errors, possibly catastrophic, due to mistaken assumptions about the decay chains involved and simultaneously improving accuracy. What is innovative is using endpoint measurements (via the wedgebox technique) to obtain a more homogeneous, well-understood sample set rather than just using said endpoints to constrain the values of the masses (here found by the mass-shell technique). The fusion of different established techniques in this manner represents a highly profitable option for LHC experimentalists who will soon have data to analyze.

hep-ph↗

arXiv2005

Pair-produced heavy particle topologies:MSSM neutralino properties at the LHC from gluino/squark cascade decays

Processes of the form $pp\to anything \to X_i X_j \to x\bar{x} + y\bar{y} (+ \slashchar{E})$ are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. $X_i$ and $X_j$ are new heavy states (with $i,j=1...n$), which may be identical or distinct; and $x\bar{x}$ and $y\bar{y}$ are necessarily distinct Standard Model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of said invariant masses, $M(x\bar{x})$ {\it vs.$$} $M(y\bar{y})$, exhibits a topology connected to the masses and specific decay chains of $X_i$ and $X_j$. Aside from relatively minor details, observed patterns consist of a collection of box and wedge shapes. This collection is model-dependent: comparison of the observed pattern to the possibilities for a specific model yields information on which new particle pair combinations are actually being produced, information beyond that extractable from conventional one-dimensional invariant mass distributions. The technique is illustrated via application to the Minimal Supersymmetric Standard Model (MSSM) process $pp \to \tilde{g}\tilde{g},\tilde{g}\tilde{q},\tilde{q}\tilde{q} \to \widetildeχ_i^0 \widetildeχ_j^0 \to e^+ e^- + μ^+ μ^- (+ \slashchar{E})$. Here the heavy states are neutralinos $\widetildeχ_i^0$ ($i=2,3,4$) -- note $\widetildeχ_1^0$ is excluded -- which are produced in gluino/squark ($\tilde{g}$/$\tilde{q}$) cascade decay chains. Even with fairly modest expectations for the LHC performance during the first few years, this method still provides substantial insight into the neutralino mass spectrum and couplings if gluino/squark masses are relatively low ($\simeq 400 \hbox{GeV}$).

hep-ph↗

arXiv2004

The Higgs Working Group: Summary Report 2003

Theoretical progress in Higgs boson production and background processes is discussed with particular emphasis on QCD corrections at and beyond next-to-leading order as well as next-to-leading order electroweak corrections. The residual theoretical uncertainties of the investigated processes are estimated in detail. Moreover, recent investigations of the MSSM Higgs sector and other extensions of the SM Higgs sector are presented. The potential of the LHC and a high-energy linear e+e- collider for the measurement of Higgs couplings is analyzed.

hep-ph↗

arXiv2003

Trilepton + top signal from chargino-neutralino decays of MSSM charged Higgs bosons at the LHC

We perform for the Large Hadron Collider (LHC) a detailed study of charged Higgs boson production via the top-bottom quark associated mode followed by decays into a chargino and a neutralino, with masses and couplings as given by the general Minimal Supersymmetric Standard Model (MSSM). We focus our attention on the region of parameter space where the charged Higgs is heavier than the top quark, with intermediate values of tan beta. In this region, the identification of charged Higgs bosons via decays into Standard Model (SM) particles has proven to be ineffective. Modelling the CMS detector, we find that a signature consisting of three hard leptons accompanied by a hadronically reconstructed top quark plus substantial missing transverse energy, which may result from charged Higgs decays into neutralinos and charginos, can be made viable over a large variety of initially overwhelming SM and MSSM backgrounds, provided MSSM input parameters are favourable: notably, a small mu parameter and light sleptons are important prerequisites. We quantify these statements by performing a fairly extensive scan of the parameter space, including realistic hadron-level simulations, and delineate some potential discovery regions.

hep-ph↗

arXiv2002

The Higgs Working Group: Summary Report (2001)

Report of the Higgs working group for the Workshop `Physics at TeV Colliders', Les Houches, France, 21 May - 1 June 2001. It contains 7 separate sections: A. Theoretical Developments B. Higgs Searches at the Tevatron C. Experimental Observation of an invisible Higgs Boson at LHC D. Search for the Standard Model Higgs Boson using Vector Boson Fusion at the LHC E. Study of the MSSM channel $A/H \to ττ$ at the LHC F. Searching for Higgs Bosons in $t\bar t H$ Production G. Studies of Charged Higgs Boson Signals for the Tevatron and the LHC

hep-ph↗

arXiv2000

Supersymmetry without R-parity : Constraints from Leptonic Phenomenology

R-parity conservation is an {\it ad hoc} assumption in the most popular version of the supersymmetric standard model. Most studies of models which do allow for R-parity violation have been restricted to various limiting scenarios. The single-VEV parametrization used in this paper provides a workable framework to analyze phenomenology of the most general theory of SUSY without R-parity. We perform a comprehensive study of leptonic phenomenology at tree-level. Experimental constraints on various processes are studied individually and then combined to yield regions of admissible parameter space. In particular, we show that large R-parity violating bilinear couplings are not ruled out, especially for large $\tanβ$.

hep-ph↗

arXiv1994

Detecting Higgs Boson Decay to Neutralinos at Hadron Supercolliders

We examine prospects for detecting the neutral Higgs bosons of minimal supersymmetric models (MSSM) when their decays into neutralino pairs are kinematically allowed. The best signature appears to be $H_h,H_p\to\tz_2\tz_2\to 4\ell +\eslt$. We argue that Standard Model contributions to this signature are negligible, and examine regions of MSSM parameter space where the four lepton mode should be observable at the Large Hadron Collider. The same signal can also come from continuum neutralino pair production. We propose a set of cuts to illustrate that the neutralino decay mode of the Higgs bosons provides a viable signal over a substantial range of model parameters, and show that it may be separable from continuum neutralino production if sufficient integrated luminosity can be accumulated.

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