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Virendra Gupta

Publications and source records attributed to Virendra Gupta.

15 recordsLinked to original sources
arXiv2018

The origin of multi-TeV flares from the nearest blazar Markarian 421

Markarian 421 is a high-peaked BL Lac object and it has undergone many strong outbursts since its discovery as a TeV source in 1992. Markarian 421 has been stud- ied intensively and was observed by various Cherenkov tele- scope arrays ever since. The outbursts of April 2004 observed by the Whipple telescope and of February 2010 by the HESS telescopes are explained well in this work by using the photohadronic model. To account for the attenuation of these high- energy gamma-rays by the extragalactic background light (EBL), we use template EBL models. The intrinsic spectrum of each epoch is different even though the high-energy protons have almost the same spectral index. We observe that this difference in intrinsic spectra is due to the change in the spectral index of the low-energy tail of the synchrotron self Compton (SSC) photons during different epochs of flaring. Our results show that the contemporaneous multiwavelength observations, particularly in the low-energy tail region of the SSC emission of the source, are important in explaining the flaring phenomenon.

astro-ph.HE↗
arXiv2016

EBL effect on the observation of multi-TeV flaring of 2009 from Markarian 501

Markarian 501 is a high-peaked BL Lacertae object and has undergone many major outburst since its discovery in 1996. As a part of the multiwavelength campaign, in the year 2009 this blazar was observed for 4.5 months from March 9 to August 1 and during the period April 17 to May 5 it was observed by both space and ground based observatories covering the entire electromagnetic spectrum. A very strong high energy $γ$-ray flare was observed on May 1 by Whipple telescope in the energy range 317 GeV to 5 TeV and the flux was about 10 times higher than the baseline flux. We use the photohadronic model complimented by the extragalactic background radiation (EBL) correction to this very high state flare and have shown that the EBL plays an important role in attenuating the very high energy flux even though Markarian 501 is in the local Universe.

astro-ph.HE↗
arXiv2013

Generalized Lorentz Transformations

Generalized Lorentz transformations with modified velocity parameter are considered. Lorentz transformations depending on the mass of the observer are suggested.The modified formula for the addition of velocities remarkably preserves the constancy of the velocity of light for all observers. The Doppler red shift is affected and can provide a test of such generalisations.

physics.gen-ph↗
arXiv2013

Recurrence in resonant transmission of one-dimensional array of delta potentials

The resonant transmission of a moving particle which interacts with an one-dimensional array of N delta-function potentials is investigated. A suitable transfer matrix formulation is used to obtain the particle transmission. We give the parameters for perfect tunnelling and the transcendental equation for the quasi-bound state energies for N = 2, 3 and 4. Conditions for perfect tunnelling and resonant transmission are discussed for arrays with arbitrary N. A model to explain how the tunnelling energy filter works in these systems is proposed here.

quant-ph↗
arXiv2013

Some results for the wave function at the origin for S-wave levels

Starting with the $S$-wave radial equation for an attractive central potential $V(r)$, we give results for the $n$ (principal quantum number) and the $μ$ (reduced mass) dependence of $R_{n0}(0)$, the $S$-wave radial wavefunction at the origin, for potentials with definite curvature.

hep-ph↗
arXiv2012

A modification of the relativistic energy-momentum relation

A modification of the accepted relativistic energy momentum relation is suggested. The new relation allows massive particles to have a maximum velocity c(m) greater than the velocity of light c. The effect of the modification suggested here would be most apparent for objects with masses nearly equal to the Planck mass.

physics.gen-ph↗
arXiv2006

Implications of measured properties of the mixing matrix on mass matrices

It is shown how the two experimentally measurable properties of the mixing matrix $V$, the asymmetry Delta(V)=|V_{12}|^2- |V_{21}|^2 of V with respect to the main diagonal and the Jarlskog invariant J(V)=Im(V_{11}V_{12}^*V_{21}^*V_{22}), can be exploited to obtain constraints on possible structures of mass matrices in the quark sector. Specific mass matrices are examined in detail as an illustration.

hep-ph↗
arXiv2005

Constraints on mass matrices due to measured property of the mixing matrix

It is shown that two specific properties of the unitary matrix $V$ can be expressed directly in terms of the matrix elements and eigenvalues of the hermitian matrix $M$ which is diagonalized by $V$. These are the asymmetry $Δ(V)= |V_{12}|^2- |V_{21}|^2$, of $V$ with respect to the main diagonal and the Jarlskog invariant $J(V)= {\rm Im}(V_{11}V_{12}^* V_{21}^* V_{22})$. These expressions for $Δ(V)$ and $J(V)$ provide constraints on possible mass matrices from the available data on $V$.

hep-ph↗
arXiv2005

On tetraquark meson states

It is suggested that the narrow meson state seen in the the SELEX experiment is a $(c\bar{s} s\bar{s})$ tetraquark state. Characteristics of other possible tetraquarks formed out of $c$ and $s$ quarks and antiquarks are considered.

hep-ph↗
arXiv2004

Predictions for hadron polarizations and left-right asymmetry in inclusive reactions involving photons

A phenomenological model which has had some success in explaining polarization phenomena and left-right asymmetry in inclusive proton-proton scattering is considered for reactions involving photons. In particular, the reactions (a) $ γ+ p \to H + X;$ (b) $γ+ p (\uparrow) \to π^{\pm} + X $ and (c) $p(\uparrow) + p \to γ+ X$ are considered where $γ=$ resolved photon and hyperon $ H = Λ^0, Σ^{\pm}$ etc. Predictions for hyperon polarization in (a) and the asymmetry (in (b) and (c)) provide further tests of this particular model. Feasibility of observing (b) at HERA and the effect of the polarization of the sea in the proton in $p (\uparrow) + p \to π^{\pm} + X$ is briefly discussed.

hep-ph↗
arXiv2003

Is the quark- mixing matrix moduli symmetric?

If the unitary quark- mixing matrix, $V$, is moduli symmetric then it depends on three real parameters. This means that there is a relation between the four parameters needed to parametrize a general $V$. It is shown that there exists a very simple relation involving $|V_{11}|^2, |V_{33}|^2,\orh $ and $\oet$. This relation is compared with the present experimental data. It is concluded that a moduli symmetric $V$ is not ruled out.

hep-ph↗
arXiv2002

Parametrization of the quark mixing matrix involving its eigenvalues

A parametrization of the $3\times 3$ Cabibbo-Kobayashi-Maskawa matrix, $V$, is presented in which the parameters are the eigenvalues and the components of its eigenvectors. In this parametrization, the small departure of the experimentally determined $V$ from being moduli symmetric (i.e. $|V_{ij}|=|V_{ji}|$) is controlled by the small difference between two of the eigenvalues. In case, any two eigenvalues are equal, one obtains a moduli symmetric $V$ depending on only three parameters. Our parametrization gives very good fits to the available data including CP-violation. Our value of $\sin 2β\approx 0.7$ and other parameters associated with the ` unitarity triangle' $V_{11}V_{13}^{*}+V_{21}V_{23}^{*}V_{31}V_{33}^{*}=0$ are in good agreement with data and other analyses.

hep-ph↗
arXiv2002

Predictions for the unitarity triangle angles in a new parametrization

A new approach to the parametrization of the CKM matrix, $V$, is considered in which $V$ is written as a linear combination of the unit matrix $I$ and a non-diagonal matrix $U$ which causes intergenerational-mixing, that is $V=\cosθI+i\sinθU$. Such a $V$ depends on 3 real parameters including the parameter $θ$. It is interesting that a value of $θ=π/4$ is required to fit the available data on the CKM-matrix including CP-violation. Predictions of this fit for the angles $α$, $β$ and $γ$ for the unitarity triangle corresponding to $V_{11}V^*_{13} + V_{21} V^*_{23} +V_{31}V^*_{33} =0$, are given. For $θ$=$π/4$, we obtain $α=88.46^\circ$, $β=45.046^\circ$ and $γ=46.5^\circ$. These values are just about in agreement, within errors, with the present data. It is very interesting that the unitarity triangle is expected to be approximately a right-angled, isosceles triangle. Our prediction $\sin 2β= 1$ is in excellent agreement with the value $0.99\pm 0.15\pm 0.05$ reported by the Belle collaboration at the Lepton-Photon 2001 meeting.

hep-ph↗
arXiv2001

A new parametrization of the neutrino mixing matrix for neutrino oscillations

In this paper we study three active neutrino oscillations, favored by recent data from SuperK and SNO, using a new parametrization of the lepton mixing matrix $V$ constructed from a linear combination of the unit matrix $I$, and a hermitian unitary matrix $U$, that is, $V = \cosθI + i\sin θU$. There are only three real parameters in $V$ including the parameter $θ$. It is interesting to find that experimental data on atmospheric neutrino dictates the angle $θ$ to be $π/4$ such that the $ν_μ$ and $ν_τ$ mixing is maximal. The solar neutrino problem is solved via the MSW effect with a small mixing angle, with $U$ depending on one small parameter $ε$. The resulting mixing matrix with just two parameters ($θ$ and $ε$) predicts that the oscillating probabilities for $ν_e\to ν_μ$ and $ν_e \to ν_τ$ to be equal and of the order $2ε^2 = (0.25\sim 2.5)\times 10^{-3}$. The measurement of CP asymmetries at the proposed Neutrino Factories would also provide a test of our parametrization.

hep-ph↗