arXiv subjects

Y. Srivastava

Publications and source records attributed to Y. Srivastava.

16 recordsLinked to original sources

arXiv2015

Experimental Tests of Local Cosmological Expansion Rates

Cosmological expansion on a local scale is usually neglected in part due to its smallness, and in part due to components of bound systems (especially those bound by non-gravitational forces such as atoms and nuclei) not following the geodesics of the cosmological metric. However, it is interesting to ask whether or not experimental tests of cosmological expansion on a local scale (well within our own galaxy) might be experimentally accessible in some manner. We point out, using the Pioneer satellites as an example, that current satellite technology allows for this possibility within time scales of less than one human lifetime.

gr-qc↗

arXiv2015

A Quantum Phase Transition in the Cosmic Ray Energy Distribution

We here argue that the "knee" of the cosmic ray energy distribution at $E_c \sim 1$ PeV represents a second order phase transition of cosmic proportions. The discontinuity of the heat capacity per cosmic ray particle is given by $Δc=0.450196\ k_B$. However the idea of a deeper critical point singularity cannot be ruled out by present accuracy in neither theory nor experiment. The quantum phase transition consists of cosmic rays dominated by bosons for the low temperature phase E E_c$. The low temperature phase arises from those nuclei described by the usual and conventional collective boson models of nuclear physics. The high temperature phase is dominated by protons. The transition energy $E_c$ may be estimated in terms of the photo-disintegration of nuclei.

hep-ph↗

arXiv2014

Asymptotic High Energy Total Cross Sections and Theories with Extra Dimensions

The rate at which cross sections grow with energy is sensitive to the presence of extra dimensions in a rather model-independent fashion. We examine how rates would be expected to grow if there are more spatial dimensions than 3 which appear at some energy scale, making connections with black hole physics and string theory. We also review what is known about the corresponding generalization of the Froissart-Martin bound and the experimental status of high energy hadronic cross sections which appear to saturate it up to the experimentally accessible limit of 100 TeV. We discuss how extra dimensions can be searched for in high energy cross section data and find no room for large extra dimensions in present data. Any apparent signatures of extra dimensions at the LHC may have to be interpreted as due to some other form of new physics.

hep-ph↗

arXiv2007

Prospects for e+e- physics at Frascati between the phi and the psi

We present a detailed study, done in the framework of the INFN 2006 Roadmap, of the prospects for e+e- physics at the Frascati National Laboratories. The physics case for an e+e- collider running at high luminosity at the phi resonance energy and also reaching a maximum center of mass energy of 2.5 GeV is discussed, together with the specific aspects of a very high luminosity tau-charm factory. Subjects connected to Kaon decay physics are not discussed here, being part of another INFN Roadmap working group. The significance of the project and the impact on INFN are also discussed. All the documentation related to the activities of the working group can be found in http://www.roma1.infn.it/people/bini/roadmap.html.

hep-ex↗

arXiv2006

A new way to detect the Higgs

We describe a new technique to look for evidence of the Higgs mechanism. The usual method involves seeking evidence for the Higgs boson either directly or via the indirect effect that a virtual Higgs boson would have on a variety of Standard Model parameters. The new technique looks for Higgs field effects that are predicted to reduce the masses of heavy particles when they are in the presence of other heavy particles.

hep-ph↗

arXiv2004

A sum rule for elastic scattering

A sum rule is derived for elastic scattering of hadrons at high energies which is in good agreement with experimental data on $p\bar{p}$ available upto the maximum energy $\sqrt{s} = 2 TeV$. Physically, our sum rule reflects the way unitarity correlates and limits how large the elastic amplitude can be as a function of energy to how fast it decreases as a function of the momentum transfer. The universality of our result is justified through our earlier result on equipartition of quark and glue momenta obtained from the virial theorem for massless quarks and the Wilson conjecture

hep-ph↗

arXiv2001

Dispersive Techniques for $α_s$, $R_{had}$ and Instability of the Perturbative Vacuum

Recent dispersive techniques developed by us are applied to discuss three problems: 1. A long standing discrepan-cy between the measurements of $R(s)$ for $\sqrt{s} = (5÷7.5)GeV$ by Crystal Ball and MARK I has been analyzed and its consequences analyzed for the number of contributing quarks. 2. Noting that the perturbative $α_s$ has the wrong analyticity, analytic models consistent with asymptotic freedom (AF) and confinement have been constructed and applied to discuss $τ$ decay. 3. It is shown that AF leads to a wrong sign for $\im\big(α(s)\big)$ which signals an instability of the perturbative QCD vacuum.

hep-ph↗

arXiv2001

The Inverse Problem: Extracting Time-Like from Space-Like Data

A practical strategy is presented and successfully implemented to determine form factors in the time-like but unphysical (below threshold) region using dispersion relations, in a model independent way without any bias towards expected resonances. Space and time-like data have been employed along with a regularization scheme to unfold and solve the integral equations. Remarkably, resonance structures with peaks for the $ρ(770)$, $ρ'(1600)$ and a structure near the $N\bar N$ threshold are automatically generated. The $Φ$ peak is invisible thus refuting suggestions about any sizeable $s\bar s$ content in the nucleon.

hep-ph↗

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.

hep-ph↗

arXiv2000

Resolution of a long standing discrepancy in R with spin zero quarks

A previously successful dispersive method has been applied to understand different values for $R(\sqrt{s} = 5 ÷7.5 GeV)$ obtained by MARK I and Crystal Ball collaborations. We compute $R$ in the disputed region with data from outside this region and asymptotic behavior given by the standard model with 5 quark flavors, and find agreement with the Crystal Ball result. On the other hand, the MARK I data are reproduced if we augment the asymptotic behavior with contributions from a single spin zero quark of charge ($ -1/3$). The visible hadronic fragments from such scalar quarks are not likely to produce predominantly pure 2-jet events at such low energies. Hence, such decay modes may have been removed by the Crystal Ball energy imbalance cuts in their definition of hadronic events but not in MARK I events, thus accounting for the discrepancy in the two results. Upper bounds on spin zero quark production at LEP through $Z$ decay data are used to estimate the mixing angle between $T_3\ = -1/2$ and $T_3 = 0$ scalar quarks. Recent negative results about spin zero quarks from CLEO are critically examined. We briefly discuss diquark production hypothesis and find it very unlikely to explain the discrepancy.

hep-ph↗

arXiv1999

Stopped Muon Decay Lifetime Shifts due to Condensed Matter

Up to second order in alpha, vacuum electro-magnetic corrections to weak interaction induced charged particle lifetimes have been previously studied. In the laboratory, stopped muon lifetimes are measured in a condensed matter medium whose radiation impedance differs from that of the vacuum. The resulting condensed matter corrections to first order in $α$ dominate those vacuum radiative corrections (two photon loops) which are second order in alpha.

hep-ph↗

arXiv1998

Total Widths And Slopes From Complex Regge Trajectories

Maximally complex Regge trajectories are introduced for which both Re $α(s)$ and Im $α(s)$ grow as $s^{1-ε}$ ($ε$ small and positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to $ε$) goes to zero. A scaling formula for the total widths emerges: $Γ_{TOT}/M\to$ constant for large M, in very good agreement with data for mesons and baryons. The unitarity corrections also enhance the space-like slopes from their time-like values, thereby resolving an old problem with the $ρ$ trajectory in $πN$ charge exchange. Finally, the unitarily enhanced intercept, $α_ρ\approx 0.525$, \nolinebreak is in good accord with the Donnachie-Landshoff total cross section analysis.

hep-ph↗

arXiv1997

Hadronic Masses and Regge Trajectories

A comprehensive phenomenological analysis of experimental data and some theoretical models is presented here (for mesons) to critically discuss how Regge trajectory parameters depend on flavor. Through analytic continuation of physical trajectories (obtained from resonance data) into the space like region, we derive the suppression factor for heavy flavor production. The case of our D Regge exchange, both for D and $Λ_c$ production, is considered in some detail. Good agreement with data is reached confirming that indeed the slopes of heavier flavors decrease. This result suggests that the confinement potential has a substantial dependence on the quark masses. In a simple non-relativistic model, constrained to produce linear Regge trajectories, it is shown that a linear quark mass dependence is required (in the confinement part of the potential) in order for the slope to decrease in the appropriate way.

hep-ph↗

arXiv1997

Regge Trajectories For All Flavors

Based on available data for mesonic resonances of light, medium and heavy flavors, we have performed a global analysis to construct the corresponding linear Regge trajectories. These have been supplemented by results from various phenomenological models presented in the literature. A satisfactory formula is found for the dependence of the intercept and the slope on quark masses. We find reasonable agreement with data on production of charmed hadrons through exchange of our charmed trajectories in the space-like region. When applied to mesons containing the top quark, our results suggest the impossibility of their formation as evidenced by other independent analyses.

hep-ph↗

arXiv1995

Real and Virtual Strange Processes

Following notions of quantum mechanics as interpreted by the Copenhagen School, we make a distinction between measurements involving one or two virtual K mesons. New predictions result for the period of K oscillations at the Phi Factory.

hep-ph↗

arXiv1995

FERMIONS IN AN EXTERNAL SU(2) MAGNETIC FIELD

We consider Fermions in a constant and uniform external $SU(2)$ magnetic field. We find that the results for the energy levels depend on the choice of gauge potential. Choosing a Landau type gauge potential yields his results. On the other hand in another gauge potential, one obtains a different continuous eigenvalue spectrum.

hep-ph↗