Partha Konar

Looking for a heavy higgsino LSP in collider and dark matter experiments

Abstract A large part of the mSUGRA parameter space satisfying the WMAP constraint on the dark matter relic density corresponds to a higgsino LSP of mass ≃ 1 TeV . We find a promising signal for this LSP at CLIC, particularly with polarized electron and positron beams. One also expects a viable monochromatic γ -ray signal from its pair annihilation at the galactic center at least for cuspy DM halo profiles. All these results hold equally for the higgsino LSP of other SUSY models like the non-universal scalar or gaugino mass models and the so-called inverted hierarchy and more minimal supersymmetry models.

R-parity violation in split supersymmetry

Abstract In the recently proposed ‘split supersymmetry’ scenario, the squark and slepton masses are allowed to be at a high scale while the gauginos and higgsinos are within a TeV. We show that in a theory with broken R-parity, the parameter space of such a scenario allows a situation where the lightest neutralino is still stable on the cosmological scale and can be a dark matter candidate. We also separate the cases where (a) it may be invisible but not a dark matter candidate, or (b) it may decay showing a displaced vertex. It is also emphasized how the constraint on the simultaneous violation of baryon and lepton numbers gets relaxed in this scenario.

Invisible charginos and neutralinos from gauge boson fusion: a way to explore anomaly mediation.

We point out that vector boson fusion at the Large Hadron Collider (LHC) can lead to useful signals for charginos and neutralinos in supersymmetric scenarios where these particles are almost invisible. The proposed signals are just two forward jets with missing transverse energy. It is shown that, in this way, one can put by far the strongest constraint on the parameter space of a theory with anomaly mediated supersymmetry breaking at the LHC. In addition, scenarios where the lightest neutralinos and charginos are Higgsino-like can give signals of the above type.

Bhabha Scattering with Radiated Gravitons at Linear Colliders

We study the process e + e − → e + e − 6 at a high-energy e + e − collider, where the missing energy arises from the radiation of Kaluza-Klein gravitons in a model with large extra dimensions. It is shown that at a high-energy linear collider, this process can not only confirm the signature of such theories but can also sometimes be comparable in effectiveness to the commonly discussed channel e + e − → γ 6 E, especially for a large number of extra dimensions and with polarized beams. We also suggest some ways of distinguishing the signals of a graviton tower from other types of new physics signals by combining data on our suggested channel with those on the photon-graviton channel.

Event shape discrimination of supersymmetry from large extra dimensions at a linear collider

The production of a charged lepton (l=e,μ) pair with a large missing energy at a linear collider is discussed as a means of distinguishing the minimal supersymmetry (MSSM) scenario from that with large extra dimensions (ADD) for parameter ranges where the total cross-sections are comparable for both. Analyses in terms of event shape variables, specifically sphericity and thrust, are shown to enable a clear discrimination in this regard.

Working group report: High energy and collider physics

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.This is a summary of the projects undertaken by the working group I on high energy and collider physics.

Slepton production from gauge boson fusion

We emphasize that charged slepton pairs produced via vector-boson fusion along with two high-mass, high-pT forward and backward jets (in two opposite hemispheres) can have a higher production cross section for heavy slepton masses than that from conventional Drell-Yan production at a hadronic collider such as the CERN LHC. We analyze the signal and leading backgrounds in detail in the minimal supersymmetric standard model with conserved baryon and lepton numbers. Our investigation reveals that the mass reach of the vector-boson fusion channel is certainly an improvement over the scope of the Drell-Yan mode.

Summary of the Activities of the Working Group I on High Energy and Collider Physics

This is a summary of the projects undertaken by the Working Group I on High Energy Collider Physics at the Eighth Workshop on High Energy Physics Phenomenology (WHEPP8) held at the Indian Institute of Technology, Mumbai, January 5-16, 2004. The topics covered are (i) Higgs searches (ii) supersymmetry searches (iii) extra dimensions and (iv) linear collider.This is a summary of the projects undertaken by the working group I on high energy and collider physics.

Signals of neutralinos and charginos from gauge boson fusion at the CERN Large Hadron Collider

We point out that interesting signals of the non-strongly interacting sector of the supersymmetric standard model arise from the production of charginos and neutralinos via vector boson fusion (VBF) at the Large Hadron Collider (LHC). In particular, if R-parity is violated, the hadronically quiet signals of charginos and neutralinos through direct production get considerably suppressed. We show that in such cases, the VBF channel can be useful in identifying this sector through clean and background-free final states.

Search for associated production of Higgs with Z boson in the noncommutative Standard Model at linear colliders

We study the associated Higgs production with Z boson at future linear colliders in the framework of the minimal noncommutative standard model. Using the Seiberg–Witten map, we calculate the production cross-section considering all orders of the noncommutative parameter Θμν. We consider the effect of earth’s rotation on the orientation of Θμν with respect to the laboratory frame and thus on the total cross-section, its azimuthal distribution and rapidity distribution for the machine energy ranging from 0.5 TeV to 3 TeV corresponding to the noncommutative scale Λ ≥ 0.5TeV.