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K. Sridhar

Publications and source records attributed to K. Sridhar.

81 records · Page 5Linked to original sources
arXiv1994

$R$--Parity Violating SUSY or Leptoquarks: Virtual Effects in Dilepton Production

In the Standard Model (SM), dilepton production in hadron--hadron collisions proceeds through the conventional Drell--Yan mechanism $q \bar{q} \rightarrow l^+ l^-$ with the exchange of a gauge boson. Some extensions of the SM contain a quark--lepton contact interaction {\it via} a $q l ϕ$ Yukawa coupling, where $ϕ$ is a scalar. Theories with scalar leptoquarks and $R$--parity violating SUSY models are the most important examples of such extensions. These Yukawa couplings induce a different dynamical configuration compared to the SM ($t$-channel vs. $s$-channel) in the $q\bar{q} \rightarrow l^+l^-$ process and thus offer the possibility of being identifiable upon imposition of suitable kinematic cuts. We discuss these effects in the context of the dilepton production in the CDF experiment, and explore consequences in the forthcoming Large Hadron Collider (LHC).

hep-ph↗
arXiv1994

A possible resolution of the CDF psi^prime anomaly

We consider the contribution of radially excited 2^3P_{1,2} states to psi^prime production at the Tevatron energy. Production of these states via the conventional gluon fusion mechanism and via gluon and charm quark fragmentation processes is considered. We find that it is possible to account for the data on psi^prime production from the CDF experiment, by taking into account the decays of these 2^3P_{1,2} states into psi^prime.

hep-ph↗
arXiv1994

J/psi+gamma Production at the Tevatron Energy

We study the process $\bar p p \rightarrow J/ψ+ γ+X$ at the Tevatron energy ($\sqrt{s} = 1.8$~TeV). The perturbative QCD contributions to this process from the gluon-fusion and the fragmentation mechanisms are computed. For the entire range of $p_T$ that can be probed at the Tevatron, the fusion contribution is found to be dominant. Consequently the QCD prediction for this process has better precision than the purely hadronic production of $J/ψ$. An experimental study of this process at the Tevatron will help to clarify several aspects of quarkonium production at large $p_T$.

hep-ph↗
arXiv1994

Fragmentation contribution to quarkonium production in hadron collision

We compute the contributions due to gluon and heavy-quark fragmentation to quarkonium production at large transverse momentum in $\bar p p$ and $p p$ collisions. For inclusive $J/ψ$ production, there is a large contribution from the $g \rightarrow χ_c$ fragmentation. At large $p_T$, this is comparable to the conventional charmonium model prediction via gluon fusion at the ISR and dominates over the latter at the Tevatron energy. This may help to explain, at least partly, the large $J/ψ$ production cross-section recently observed by the CDF experiment. However, the fragmentation contribution to $ψ^{\prime}$ production is not large enough to explain the corresponding CDF data. We also present the results for $Υ$ production at ISR and Tevatron energies.

hep-ph↗
arXiv1994

Bounds on the Masses and Couplings of Leptoquarks from Leptonic Partial Widths of the Z

The vertex corrections to the leptonic partial widths of the $Z$ induced by leptoquarks that couple leptons to the top quark are considered. We obtain stringent bounds on the parameter space of the masses and Yukawa couplings of these leptoquarks, using the latest information on the $Z \rightarrow l^+l^-$ decay widths measured at LEP. Leptoquarks coupling with electroweak strength to top quarks are constrained to be heavier than several hundred GeV, at 95$\%$ C.L. As a consequence, such leptoquarks cannot make a significant contribution to lepton asymmetries, $τ$ polarisation asymmetries or $A_{LR}$.

hep-ph↗
arXiv1993

QCD calculation of J/psi+gamma mass distributions

We compute the J/psi+gamma invariant-mass distributions from the QCD subprocess g + g --> J/psi+gamma. At large masses, this subprocess is the dominant mechanism for J/psi+gamma production, and data could provide a good test of QCD. The mass distribution peaks at relatively small masses (3.4 - 4.0 GeV) and the subprocess could, therefore, represent a significant QCD background to J/psi+gamma decay of heavier charmonia. We also analyze the J/psi angular distribution in the J/psi+gamma rest frame.

hep-ph↗
arXiv1993

Non-perturbative unification in the light of LEP results

We consider an alternative to conventional GUTs originally proposed by Maiani, Parisi and Petronzio, where owing to the existence of extra fermion generations at some intermediate scale, the gauge couplings become large at high energies. We first comment on how the non- supersymmetric version of this scenario is ruled out; we then consider the two-loop evolution of the couplings in the supersymmetric extension of this scenario, and check whether such a scenario is feasible in the light of the precies values of couplings now available from LEP.

hep-ph↗
arXiv1992

Looking for the gluonic EMC effect in associated $J/ψ$ + $γ$ production

We study the associated production of $ J/ψ + γ$ in fixed-target experiments with nuclear targets as well as at the relativistic heavy-ion collider (RHIC). We find that this process affords a very clean probe of $ρ_g$, the ratio of gluon density in a heavy nucleus to that of a proton. The combined $x$ range thus available can be used to discriminate between the predictions of different models of the EMC effect for $ρ_g$.

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