arXiv subjects

Rohini M. Godbole

Publications and source records attributed to Rohini M. Godbole.

At least 91 records · Page 5Linked to original sources

arXiv2006

Supersymmetry at the PLC

In this talk I will begin with a very brief discussion as to why TeV scale Supersymmetry forms an important subject of the studies at all the current and future Colliders. Then, I will give different examples where the Photon Linear Collider, PLC, will be able to make unique contributions. PlC's most important role is in the context of Higgs Physics, due to its ability of accurate determination of $Γ_{γγ}$ as well as the possibilities it offers for the determination of the CP property of the Higgs boson and of possible CP mixing in the Higgs sector. Further, the PLC can provide probes of SUSY in the regions of the SUSY parameter space, which are either difficult or inaccessible at the LHC and also in the $e^+e^-$ mode of the International Linear Collider (ILC).

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arXiv2006

LHC-ILC synergy

I will begin by making a few general comments on the synergy between the Large Hadron Collider (LHC) which will go in action in 2007 and the International Linear Collider (ILC) which is under planning. I will then focus on the synergy between the LHC and the PLC option at the ILC, which is expected to be realised in the later stages of the ILC program. In this I will cover the possible synergy in the Higgs sector (with and without CP violation), in the determination of the anomalous vector boson couplings and last but not the least, in the search for extra dimensions and radions.

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arXiv2006

Theoretical expectations for total cross-sections at the large hadron collider

In this note, we summarize and compare various model predictions for $pp$ total cross-section $σ_{\rm tot}^{pp}$, giving an estimate of the range of predictions for the total cross-section, $σ_{\rm tot}^{pp}$ expected at the LHC. We concentrate on the results for $σ_{\tot}^{pp}$ obtained in a particular QCD based model of the energy dependence of the total cross-section, including the effect of soft gluon radiation. We obtain the range of predictions in this model by exploring the allowed range of model parameters. We further give a handy parametrisation of these results which incidentally spans the range of various other available predictions at the LHC as well.

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arXiv2005

CP violation in Supesymmetry and the LHC

In this talk I discuss possibilities of probing the CP violation (CPV) in the Minimal Supersymmetric Standard Model (MSSM), at the LHC as well as its effects on the LHC SUSY phenomenology. In the latter case I mainly discuss its effect on the Higgs-sector and hence on Higgs Phenomenology at the LHC. After outlining the possibilities that a study of the $\ch_1 \nt_2$ production at the LHC might offer, I will summarise the effects of the CPV in MSSM on the Higgs searches at the LHC. Further, I will discuss how a study of the process $H^\pm \to W^+ ϕ_1$ may be able to plug a 'hole" in the $\tan β$-$\mh{+}$ plane, where the LEP has no sensitivity and where the searches in the usual discovery channels at the LHC are likely to fail as well.

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arXiv2005

Tau Polarization as a Probe of CP of a Light Higgs Boson

Unfortunately, we have discovered a bug in the computer program which invalidates the numerical results presented in this talk. While our formulae and the dependencies are correct, the numerical values of the asymmetries presented in the paper go down by more than two orders of magnitude. The new results will be presented elsewhere.

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arXiv2005

Tau polarization as CP diagnostic for a light Higgs boson at a photon collider

Unfortunately, we have discovered a bug in the computer program which invalidates the numerical results of our paper. While our formulae and the dependencies explained in the paper are correct, the numerical values of the asymmetries presented in the paper go down by more than two orders of magnitude. The plots and the conclusions of the paper as they stand are hence invalid and will have to be changed. We withdraw this paper till we finish this reformulation.

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arXiv2005

Synergy between the LHC and the ILC

In this talk I explain in brief the motivations behind undertaking a study of the LHC-ILC interplay. I will give information about the activities of the LHC-LC study group as well as the study group document. I will illustrate the scope of the document by taking a few examples from the document which has appeared on the archives \cite{Group:2004hn} since this talk was presented.

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arXiv2004

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.

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arXiv2004

Fermion polarization in sfermion decays as a probe of CP phases in the MSSM

The longitudinal polarization of fermions (tops and taus) produced in sfermion decays to neutralinos or charginos can be a useful tool for the determination of SUSY parameters. We discuss this fermion polarization in the context of the MSSM with complex parameters. We show that the dependence on CP-violating phases can be large and that the fermion polarization may hence be used as a sensitive probe of CP phases in the MSSM.

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arXiv2003

CP property of the Higgs at the gamma gamma colliders using $t \bar t$ production

We present results of an investigation to study CP violation in the Higgs sector in $t\bar t$ production at a $γγ$-collider, via the process $ \gamgam \ra ϕ\ra t \bar t$ where the $ϕ$ is a scalar with indeterminate CP parity. The study is performed in a model independent way parametrising the CP violating couplings in terms of six form factors $\{\Re(S_γ), \Im(S_γ), \Re(P_γ), \Im(P_γ), S_t, P_t\}$. The CP violation is reflected in the polarisation asymmetry of the produced top quark. We use the angular distribution of the decay lepton from $t/\bar t$ as a diagnostic of this polarisation asymmetry and hence of the CP mixing, after showing that the asymmetries in the angular distribution are indpendent of any CP violation in the $tbW$ vertex. We construct combined asymmetries in the initial state lepton (photon) polarization and the final state lepton charge and study how well different combinations of these form factors can be probed by measurements of these asymmetries, using circularly polarized photons. We demonstrate the feasibility of the method to probe CP violation in the Higgs sector at the level induced by loop effects in supersymmetric theories, using realistic photon spectra expected for a TESLA like $e^+ e^-$ collider. We investigate the sensitivity of our method for for different widths of the scalar as well as for the more realistic backscattered laser photon spectrum resulting from the inlcusion of the nonlinear effects.

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arXiv2003

Photon 2003: a theorist's summary and outlook

In this talk I present a summary of some of the discussions at the conference on various topics in Photon physics, selected with a view to give a theorist's perspective, of the current status and future prospects, of the developments in the field. After discussing some of the recent theoretical developments in the subject of Photon Structure function, I will focus on what the photon has helped us learn about the spin structure of a proton, aspects of perturbative and nonperturbative QCD as well as forward and diffractive physics. I will discuss the challenges that the data on heavy flavour production in the two photon reactions and in photo production, seem to have presented to the theorists. Then I discuss the direction in which photon physics is likely to go in future and what we {\em need} the photons to still tell us. I will end by talking about the newer developments in prospects for photon studies at future colliders and opportunities that these will provide us to learn about the physics beyond the Standard Model.

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arXiv2002

Study of CP Property of the Higgs at a Photon Collider using $γγ\to t\bar t\to l X $

We study possible effects of CP violation in the Higgs sector on $t\bar t$ production at a $γγ$-collider. These studies are performed in a model-independent way in terms of six form-factors $\{\Re(S_γ), \Im(S_γ), \Re(P_γ), \Im(P_γ), S_t, P_t\}$ which parametrize the CP mixing in the Higgs sector, and a strategy for their determination is developed. We observe that the angular distribution of the decay lepton from $t/\bar t$ produced in this process is independent of any CP violation in the $tbW$ vertex and hence best suited for studying CP mixing in the Higgs sector. Analytical expressions are obtained for the angular distribution of leptons in the c.m. frame of the two colliding photons for a general polarization state of the incoming photons. We construct combined asymmetries in the initial state lepton (photon) polarization and the final state lepton charge. They involve CP even ($x$'s) and odd ($y$'s) combinations of the mixing parameters. We study limits up to which the values of $x$ and $y$, with only two of them allowed to vary at a time, can be probed by measurements of these asymmetries, using circularly polarized photons. We use the numerical values of the asymmetries predicted by various models to discriminate among them. We show that this method can be sensitive to the loop-induced CP violation in the Higgs sector in the MSSM.

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arXiv2002

Exotic SUSY scenarios

In this talk I discuss some scenarios which involve small extensions of the ideas usually considered in the Minimal Supersymmetric Standard Model (MSSM). I present results of a study of the implication of non-universal gaugino masses (NGM) for the invisible decays of the lightest scalar and the correlation of the same with the relic density of the lightest supersymmetric particle (LSP) in the Universe. Further I discuss SUSY with \rpv. Decay of $\tilde χ_1^0$ in the case of dominant \rpv and \LV, trilinear $λ$ and $λ'$ couplings, and also that of $\tilde χ_1^0, \tilde χ_1^+$ caused by the bilinear \rpv, \LV couplings are discussed. The effect of the latter for the trilepton signal at the Tevatron is presented. I end with a discussion of signals of Heavy Majorana Neutrinos (HMN) at the LHC.

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arXiv2002

Measuring R-parity-violating couplings in dilepton production at the LHC

We revisit the issue of probing R-violating couplings of supersymmetric theories at hadronic colliders, particularly at the LHC. Concentrating on dimuon production, an evaluation of the optimal sensitivity to the R-violating coupling is performed through a maximum likelihood analysis. The measurement uncertainties are evaluated through a study of fully generated events processed through a fast simulation of the ATLAS detector. It is found that a host of R-violating couplings can be measured to a statistical accuracy of better than 10%, over a significant part of the m_{tilde f} -- lambda parameter space still allowed by low energy measurements. Since the bounds thus obtained do not simply scale as the squark mass, one can do significantly better at the LHC than at the Tevatron. The same analysis can also be extended to assess the reach of the LHC to effects due to any non-SM structure of the four-fermion amplitude, caused by exchanges of new particles with different spins such as leptoquarks and gravitons that are suggested by various theoretical ideas.

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arXiv2002

Physics Potential of the Next Generation Colliders

In this article I summarize some aspects of the current status of the field of high energy physics and discuss how the next generation of high energy colliders will aid in furthering our basic understanding of elementary particles and interactions among them, by shedding light on the mechanism for the spontaneous breakdown of the Electroweak Symmetry.

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arXiv2001

Total Cross Sections

A unified approach to total cross-sections, based on the QCD contribution to the rise with energy, is presented for the processes $pp$, $p{\bar p}$, $γp, γγ, e^+e^- \to hadrons$. For proton processes, a discussion of the role played by soft gluon summation in taming the fast rise due to mini-jets is presented. For photon-photon processes, a comparison with other models indicates the need for precision measurements in both the low and high energy region, likely only with measurements at future Linear Colliders.

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arXiv2001

$σ^{tot}_{ee γγ}$ at $e^+e^-$ colliders}

In this talk I briefly summarize different models for $σ^{tot}_{2 γ}$ ($e^+e^- \to γγ\to$ hadrons) and contrast model predictions with the data. I will then discuss the capability of the future $e^+e^-$ and $γγ$ colliders to distinguish between various models and end with an outlook for future work.

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arXiv2001

SUSY and SUSY Breaking Scale at the Linear Collider

After summarising very briefly the key features of different model predictions for sparticle masses and their relation with the supersymmetry (SUSY) breaking scales and parameters, I discuss the capabilities of an $e^+ e^-$ Linear Collider (LC) with $\sqrt{s} \geq$ 500 GeV for precision measurements of sparticle properties. Then I focus on the lessons one can learn about the scale and mechanism of SUSY breaking from these measurements and point out how LC can crucially complement and extend the achievements of the LHC. I end by mentioning what would be the desired extensions in the type/energy of the colliding particles and their luminosity from the point of view of SUSY investigations.

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