arXiv subjects

Yogendra N. Srivastava

Publications and source records attributed to Yogendra N. Srivastava.

13 recordsLinked to original sources

arXiv2025

Very high energy cosmic ray particles from the Kerr black hole at the galaxy center

Conventional general relativity supplies the notion of a vacuum tension and thus a maximum force $F_{max}=c^4/4G\approx\ 3\times 10^{43}$ Newtons, that is realized for a black hole. In conjunction with the Wilson area rule, we are thus led to the surface confinement of the mass of a black hole analogous to the surface confinement of quarks. The central result of our paper is that PeV scale protons exist on the surface of a Kerr black hole residing at our galactic center that is in concert with the HAWC Collaboration result of a PeVatron at the galactic center.

astro-ph.HE↗

arXiv2020

About soft photon resummation

The first time one of us (G.P.) encountered Earle was in Summer 1966, when she was directed to study Earle's papers on radiative corrections to quasi-elastic electron scattering. The suggestion had come from Bruno Touschek, at the time head of the theoretical physics group at the Frascati National Laboratories near Rome. About the same time, Earle came from MIT to visit University of Rome and Frascati. G.P. was a young post-graduate, who had studied Earle's papers and was awed by his already impressive scientific figure. After almost 40 years had passed, Earle visited Italy with his wife Ruth, making Frascati their base for an extended visit of almost a month. They were housed in what was then the laboratory hostel for foreign visitors, a small villa higher up above the hill, toward the town of Frascati. Since then, we became close friends, a friendship which included both his family and ours, and which has been very important for us. In memory of that first visit and in gratitude for the many years of friendship, we will tell here a story of infrared radiative corrections to charged particle scattering, to which Earle's papers gave an important contribution.

physics.hist-ph↗

arXiv2019

Modeling Double Parton Scattering at LHC

We examine present data for double parton scattering at LHC and discuss their energy dependence from its earliest measurements at the ISR. Different models for the effective cross-section are considered and their behavior studied for a variety of selected final states. We point out that data for pp ->4 jets or pp -> quarkonium pair indicate the effective cross-section to increase with energy. We compare this set of data with different models, including one inspired by our soft gluon resummation model for the impact parameter distribution of partons.

hep-ph↗

arXiv2017

Inelastic cross-section and Survival Probabilities at LHC in mini-jet models

Recent results for the total and inelastic hadronic cross-sections from LHC experiments are compared with predictions from a single channel PDF driven eikonal mini-jet model and from an empirical model. The role of soft gluon resummation in the infrared region in taming the rise of mini-jets and their contribution to the increase of the total cross-sections at high energies are discussed. Survival probabilities at LHC, whose theoretical estimates range from circa 10 percent to a few per mille, will be estimated in this model and compared with results from QCD inspired models and from multi channel eikonal models. We revisit a previous calculation and examine the origin of these discrepancies.

hep-ph↗

arXiv2016

Introduction to the physics of the total cross-section at LHC: A Review of Data and Models

This review describes the development of the physics of hadronic cross sections up to recent LHC results and cosmic ray experiments. We present here a comprehensive review - written with a historical perspective - about total cross-sections from medium to the highest energies explored experimentally and studied through a variety of methods and theoretical models for over sixty years. We begin by recalling the analytic properties of the elastic amplitude and the theorems about the asymptotic behavior of the total cross-section. A discussion of how proton-proton cross-sections are extracted from cosmic rays at higher than accelerator energies and help the study of these asymptotic limits, is presented. This is followed by a description of the advent of particle colliders, through which high energies and unmatched experimental precisions have been attained. Thus the measured hadronic elastic and total cross-sections have become crucial instruments to probe the so called soft part of QCD physics, where quarks and gluons are confined, and have led to test and refine Regge behavior and a number of diffractive models. As the c.m. energy increases, the total cross-section also probes the transition into hard scattering describable with perturbative QCD, the so-called mini-jet region. Further tests are provided by cross-section measurements of gamma p, gamma*p and gamma* gamma* for models based on vector meson dominance, scaling limits of virtual photons at high Q^2 and the BFKL formalism. Models interpolating from virtual to real photons are also tested.

hep-ph↗

arXiv2014

Infrared Gluon Resummation and pp total cross-sections

We address here the problem of describing both the total and the elastic proton-proton cross-section, through the four outstanding features of hadron scattering: (i) the optical point; (ii) the forward peak, (iii) the dip and (iv) the subsequent descent at larger momentum transfers. These issues are discussed through an eikonal model for the elastic amplitude where the matter distribution in impact parameter space is given by resummed soft gluons down into the infrared (IR) region. The asymptotic growth of the total cross-section is obtained in a mini-jet model and the taming (saturation) at high energies is related to confinement realized here through an IR singular strong coupling constant alpha_s(Q^2). We present an ansatz that links the IR singularity of alpha_s(Q^2) to that of asymptotic freedom (AF) (at lowest order). Through this model, we illustrate the problems that arise in a generic one-channel eikonal model employed for a description of the measured differential elastic cross-section at LHC7.

hep-ph↗

arXiv2014

An empirical model for $pp$ scattering and geometrical scaling

We present the result of an empirical model for elastic $pp$ scattering at LHC which indicates that the asymptotic black disk limit ${\cal R}=\sigel/\sigtot\rightarrow1/2$ is not yet reached and discuss the implications on classical geometrical scaling behavior. We propose a geometrical scaling law for the position of the dip in elastic $pp$ scattering which allows to make predictions valid both for intermediate and asymptotic energies.

hep-ph↗

arXiv2013

Elastic pp scattering from the optical point to past the dip: an empirical parametrization from ISR to LHC

We describe the main features of recent LHC data on elastic pp scattering through a simple parametrization to the amplitude, inspired by a model proposed by Barger and Phillips in 1973, comprising of two exponentials with a relative phase. Despite its simplicity, this parameterization reproduces two essential aspects of the elastic differential cross section, the well known precipitous descent in the forward direction and a sharp `dip' structure. To include a complete description of data sets near -t=0, we correct the original parametrization. We examine two possibilities, the presence of the two-pion threshold singularity or a multiplicative factor reflecting the proton form factor. We find good descriptions of LHC7 and ISR data in either case. The form factor model allows simple predictions for higher energies through asymptotic theorems and asymptotic sum rules in impact parameter space. We present predictions for this model at higher LHC energies, which can be used to test whether asymptotia is reached. The black disk limit in this model is seen to be reached only for energies near 10^6 TeV.

hep-ph↗

arXiv2012

Checks of asymptotia in pp elastic scattering at LHC

We parametrize TOTEM data for the elastic differential pp cross section at sqrt(s)=7 TeV in terms of two exponentials with a relative phase. We employ two previously derived sum rules for pp elastic scattering amplitude in impact parameter space to check whether asymptotia has been reached at the LHC. A detailed study of the TOTEM data for the elastic differential cross section at sqrt(s)=7 TeV is made and it is shown that, within errors, the asymptotic sum rules are satisfied at LHC. We propose to use this parametrization to study forthcoming higher energy data.

hep-ph↗

arXiv2011

Total and inelastic cross-sections at LHC at CM energy of 7 TeV and beyond

We discuss expectations for the total and inelastic cross-sections at LHC CM energies $\sqrt{s}\ =\ 7\ TeV$ {and $ 14\ TeV$} obtained in an eikonal minijet model augmented by soft gluon $k_t$-resummation, which we describe in some detail. We present a band of predictions which encompass recent LHC data and suggest that the inelastic cross-section described by two channel eikonal models include only uncorrelated processes. We show that this interpretation of the model is supported by the LHC data.

hep-ph↗

arXiv2010

Modeling pion and proton total cross-sections at LHC

To settle the question whether the growth with energy is universal for different hadronic total cross-sections, we present results from theoretical models for pion-proton, proton-proton and proton-antiproton total cross-sections. We show that present and planned experiments at LHC can differentiate between different models, all of which are consistent with presently available (lower energy) data. This study is also relevant for the analysis of those very high energy cosmic ray data which require reliable pion-proton total cross-sections as seeds. A preliminary study of the total pion-pion cross-sections is also made.

hep-ph↗

arXiv2010

Soft gluon resummation in the infrared region and the Froissart bound

We describe the taming effect induced by soft gluon $k_t$-resummation on the rapid rise of QCD mini-jet contributions to the total cross-sections.This results from an eikonal model in which the rise of the total cross-section is due to mini-jet contribution. We perform the calculation with current Parton Density Functions (PDFs). The impact parameter distribution we use is obtained as the Fourier transform of the resummed $k_t$-distribution of soft gluons emitted from the initial state during the collision.The emission, which is energy dependent, destroys the initial collinearity of partons.In this model, the strong power-like rise due to the increasing number of low-x gluon collisions is tamed by the acollinearity induced by soft gluon kt-resummation down to zero gluon momenta. It explicitly links a singular soft gluon coupling in the infrared region to the behaviour dictated by the Froissart bound for the total cross-section. The model describes well both proton and photon processes at present accelerator energies and gives predictions in the TeV range. For photons the model predictions agree with fits by Block and Halzen based on Finite Energy Sum Rules (FESR) at low energy and an asymptotic behaviour consistent with the Froissart bound.

hep-ph↗

arXiv1994

Bounds on Compositeness from Neutrinoless Double Beta Decay

Assuming the existence of a heavy Majorana neutral particle arising from a composite model scenario we discuss the constraints imposed by present experimental limits of half-life neutrinoless double beta decay $(0νββ) $ measurements on the coupling of the heavy composite neutrinos to the gauge bosons. For neutrino masses $M_N = 1 $ TeV we obtain a rather weak lower bound on the compositeness scale: $Λ\ge 0.23 $ TeV.

hep-ph↗