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R. M. Godbole

Publications and source records attributed to R. M. Godbole.

At least 55 records · Page 3Linked to original sources
arXiv2005

Probing the CP-violating light neutral Higgs in the charged Higgs decay at the LHC

The CP-violating MSSM allows existence of a light neutral Higgs boson ($M_{H_1} \lapp 50$ GeV) in the CPX scenario in the low $\tan β(\lapp 5)$ region, which could have escaped the LEP searches due to a strongly suppressed $H_1 Z Z$ coupling. This parameter space corresponds to a relatively light $H^\pm$ ($M_{H^\pm} < M_t$), which is predicted to decay dominantly into the $W H_1$ channel. Thus one expects to see a striking $t \bar t$ signal at the LHC, where one of the top quarks decays into the $bb \bar b W$ channel, via $t \to b H^\pm, H^\pm \to W H_1$ and $H_1 \to b \bar b$. The characteristic correlation between the $b \bar b$, $b \bar b W$ and $b b \bar b W$ invariant mass peaks is expected to make this signal practically free of the SM background. Our parton level Monte Carlo simulation yields upto 5000 events, for ${\cal L} = 30$ fb$^{-1}$, over the parameter space of interest, after taking into account the b-tagging efficiency for three or more b-tagged jets.

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arXiv2005

Using Tau Polarization to Discriminate between SUSY Models and Determine SUSY Parameters at ILC

In many SUSY models the first SUSY signal in the proposed International Linear Collider is expected to come from the pair production of $\tildeτ_1$, followed by its decay into $τ$+LSP. We study a simple and robust method of measuring the polarization of this $τ$ in its 1-prong hadronic decay channel,and show how it can be used to discriminate between SUSY models and to determine SUSY parameters.

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arXiv2005

Deep inelastic scattering and forward neutral pion production at NLO

We present a detailed phenomenological study of forward hadron neutral pion production in deep inelastic scattering, with both the direct and the resolved contributions calculated to NLO accuracy. A comparison of the theoretical predictions for the various distributions with the H1 data and a study of stability of the QCD predictions under changes of scales is the focus of this study. We obtain a very good overall description of the recent H1 data with the choice of scale Q^2 + E^2_{perp}, in contrast to the (Q^2 + E^2_{perp})/2 required earlier when the resolved contribution was included only at LO accuracy. We find a more modest variation of the predictions, as the scale is changed from (Q^2 + E^2_{perp})/2 to 2(Q^2 + E^2_{perp}), as compared to the case where the resolved contribution was included only at LO accuracy. This variation is of the order of the rather large experimental errors. Unfortunately, this fact prevents us from concluding that perturbation theory gives an unambiguous prediction for forward particle production in deep inelastic scattering. However, the overall success of perturbative QCD in explaining the small x_{Bj} data means that perhaps a full resummation of the BFKL ladder is not called for. We notice the need for rather large resolved contributions to explain the data at low x_{Bj} even at somewhat larger Q^2 values.

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arXiv2004

Total Cross-Sections : Cross-Talk between HERA, LHC and LC

We discuss the need to compare total cross-section measurements at LHC and HERA with each other and with available models in order to obtain a more precise prediction of the total hadronic cross-section at the future Linear Collider, thus leading to a better estimate of the hadronic background.

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arXiv2004

CP Studies of the Higgs Sector

The CP structure of the Higgs sector will be of great interest to future colliders. The measurement of the CP properties of candidate Higgs particles will be essential in order to distinguish models of electroweak symmetry breaking, and to discover or place limits on CP-violation in the Higgs sector. In this report we briefly summarize various methods of determining the CP properties of Higgs bosons at different colliders and identify areas where more study is required. We also provide an example of a synergy between the LHC, an e+e- Linear Collider and a Photon Collider, for the examination of CP-violation in a Two-Higgs-Doublet-Model.

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arXiv2004

An NLO calculation of the electroproduction of large-E_\bot hadrons

We present a Next-to-Leading Order calculation of the cross section for the leptoproduction of large-$E_{\bot}$ hadrons and we compare our predictions with H1 data on the forward production of $π^0$. We find large higher order corrections and an important sensitivity to the renormalization and factorization scales. These large corrections are shown to arise in part from BFKL-like diagrams at the lowest order.

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arXiv2003

Photon Total Cross-sections

We discuss present predictions for the total $γγ$ and $γp $ cross-sections, highlighting why predictions differ. We present results from the Eikonal Minijet Model and improved predictions based on soft gluon resummation.

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arXiv2003

Search for `invisible' Higgs signals at LHC via Associated Production with Gauge Bosons

A light Higgs boson with substantial branching ratio into invisible channels can occur in a variety of models with: light neutralinos, spontaneously broken lepton number, radiatively generated neutrino masses, additional singlet scalar(s) and/or right handed neutrinos in the extra dimensions of TeV scale gravity. We study the observability of the WH and ZH modes at LHC with H decaying invisibly, by carrying out a detailed simulation with two event generators HERWIG and PYTHIA and realistic detector simulations (GETJET and CMSJET). We find that the signal with `single lepton plus missing $E_T$' resulting from WH production suffers from a very large background due to the (off-shell) $W^{*}$ production via the Drell-Yan process. In contrast, the ZH mode provides a clean signal in the `dilepton plus missing $E_T$' channel. By exploiting this second signature, we show that invisible branching ratios of Higgs bosons, ${BR}_{inv}$, larger than $\sim 0.42(0.70)$ can be probed at 5$σ$ level for $M_H = 120$(160) GeV respectively, assuming an accumulated luminosity of L=100 fb$^{-1}$.

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arXiv2003

Hadronic Cross-sections in two photon Processes at a Future Linear Collider

In this note we address the issue of measurability of the hadronic cross-sections at a future photon collider as well as for the two-photon processes at a future high energy linear $e^+e^-$ collider. We extend, to higher energy, our previous estimates of the accuracy with which the \gamgam\ cross-section needs to be measured, in order to distinguish between different theoretical models of energy dependence of the total cross-sections. We show that the necessary precision to discriminate among these models is indeed possible at future linear colliders in the Photon Collider option. Further we note that even in the $e^+e^-$ option a measurement of the hadron production cross-section via \gamgam processes, with an accuracy necessary to allow discrimination between different theoretical models, should be possible. We also comment briefly on the implications of these predictions for hadronic backgrounds at the future TeV energy $e^+e^-$ collider CLIC.

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arXiv2003

Predictions for the $γγ$ total cross-section in the TeV region: an update

In this talk we present an update of model predictions for the $γγ$ total cross-section in the TeV region. The update includes preliminary results for $γγ$ cross-sections using the Bloch-Nordsieck model for the overlap function of the partons in the transverse space, use of the CJLK parametrisation of the photonic parton densities that has recently become available and extension to the higher $γγ$ energies relevant to the planned CLIC collider.

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arXiv2002

Probing the CP of the Higgs at a $γγ$ collider using $γγ\to t \bar t \to lX$

We present results of an investigation to study CP violation in the Higgs sector in $t\bar t$ production at a $γγ$-collider. This is done 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 parameterize the CP mixing in Higgs sector. The angular distribution of the decay lepton from $t/\bar t$ is shown to be independent of any CP violation in the $tbW$ vertex. Hence it can be used as a diagnostic of the CP mixing. We study how well one can probe different combinations of the form factors by measurements of the combined asymmetries that we construct, in the initial state lepton (photon) polarization and the final state lepton charge, using only circularly polarized photons. We show that the method can be sensitive to loop-induced CP violation in the Higgs sector in the MSSM.

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arXiv2002

Three-body decays of $\tilde χ_1^0$ in $\rp$ models with dominant $λ$ and $λ'$ couplings

Decays of the lightest neutralino are studied in $R_p$-violating models, with operators $λ^\prime L Q D^c$ and $λL L E^c$ involving third-generation matter fields and with dominant $λ^\prime$ and $λ$ couplings. Decays with the top-quark among the particles produced are considered, in addition to those with an almost massless final state. Phenomenological analyses for examples of both classes of decays are presented. No specific assumption on the composition of the lightest neutralino is made. Our formulae can easily be generalized to study decays of heavier neutralinos. We also discuss effects of the $\rp$ decays of the $\tilde χ_1^0$ on the possible faking of the $H^\pm$ signal at the LHC by the recently pointed out $\tilde τ\bar b t$ production through $λ'_{333}$ coupling.

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arXiv2002

Lightest-neutralino decays in R_p-violating models with dominant lambda^{prime} and lambda couplings

Decays of the lightest neutralino are studied in R_p-violating models with operators lambda^{prime} L Q D^c and lambda L L E^c involving third-generation matter fields and with dominant lambda^{prime} and lambda couplings. Generalizations to decays of the lightest neutralino induced by subdominant lambda^{prime} and lambda couplings are straightforward. Decays with the top-quark among the particles produced are considered, in addition to those with an almost massless final state. Phenomenological analyses for examples of both classes of decays are presented. No specific assumption on the composition of the lightest neutralino is made, and the formulae listed here can be easily generalized to study decays of heavier neutralinos. It has been recently pointed out that, for a sizable coupling lambda^{prime}_{333}, tau-sleptons may be copiously produced at the LHC as single supersymmetric particles, in association with top- and bottom-quark pairs. This analysis of neutralino decays is, therefore, a first step towards the reconstruction of the complete final state produced in this case.

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arXiv2002

Invisible Decays of the Supersymmetric Higgs and Dark Matter

We discuss effects of the light sparticles on decays of the lightest Higgs in a supersymmetric model with nonuniversal gaugino masses at the high scale, focusing on the `invisible' decays into neutralinos. These can impact significanlty the discovery possibilities of the lightest Higgs at the LHC. We show that due to these decays, there exist regions of the $M_2-μ$ space where the B.R. $(h \to γγ)$ becomes dangerously low even after imposing the LEP constraints on the sparticle masses, implying a possible preclusion of its discovery in the $γγ$ channel. We find that there exist regions in the parameter space with acceptable relic density and where the ratio ${B.R. (h \to γγ)_{SUSY} \over B.R. (h \to γγ)_{SM}}$ falls below 0.6, implying loss of signal in the $γγ$ channel. These regions correspond to $\tilde χ_1^+, \tilde χ_2^0$ masses which should be accessible already at the Tevatron. Further we find that considerations of relic density put lower limit on the U(1) gaugino mass parameter $M_1$ independently of $μ, \tan β$ and $m_0$.

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arXiv2002

Total Cross-sections

We examine the energy dependence of total cross-sections for photon processes and discuss the QCD contribution to the rising behaviour

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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

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arXiv2001

J/ψproduction through resolved photon processes at e+ e- colliders

We consider J/psi photoproduction in e+ e- as well as linear photon colliders. We find that the process is dominated by the resolved photon channel. Both the once-resolved and twice-resolved cross-sections are sensitive to (different combinations of) the colour octet matrix elements. Hence, this may be a good testing ground for colour octet contributions in NRQCD. On the other hand, the once-resolved J/psi production cross-section, particularly in a linear photon collider, is sensitive to the gluon content of the photon. Hence these cross-sections can be used to determine the parton distribution functions, especially the gluon distribution, in a photon, if the colour octet matrix elements are known.

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