119227274
Strange mass corrections to hyperonic semi-leptonic decays in statistical model
We study the spin distribution, weak decay coupling constant ratios for strange baryon octets with SU(3) breaking effects. Baryon is taken as an ensemble of quark-gluon Fock states in the sea with three valence quarks with definite spin, color and flavor quantum numbers. We apply the statistical model to calculate the probabilities of each Fock states, to analyze the impact of SU(3) breaking in the weak decays. The symmetry breaking effects are studied in terms of a parameter “r ” whose best-fit value is obtained from the experimental data of semi-leptonic weak decay coupling constant ratios. We suggest the dominant contribution from H1G8 (sea with spin one and color octet) where symmetry breaking corrections lead to the deviations in the value of the axial-vector matrix elements ratio F/D from experimental values by 17%. We conclude that symmetry breaking also significantly affects the polarization of quark in strange baryons.
119240557
Sea-quark and gluonic contributions to strange baryons and its properties
We treat the hadrons as an ensemble of quark-gluon Fock states where contributions from sea-quarks and gluons can be studied in detail for the properties of low lying baryons. Statistical model is applied to calculate individual probabilities from various scalar, vector and tensor sea components in flavour, spin and colour subspaces for each quark-gluon Fock state. The mass of strange quark is imposed in terms of constraints to the availability of strange quarks in the sea and free energy of gluons in conformity with experimental indications. We calculate multiplicities for different sets of Fock states to compute the role of strange sea for cascade doublet Ξ+ and Ξ0. The low energy properties like magnetic moment, weak decay matrix elements and axial coupling constant ratios have been studied. The incorporation of strange quark gluon sea is discussed and they are found to affect the results by almost 46%.The results provide deeper understanding for baryon structure thereby motivating experiments for further inspection, especially the spin distribution among the quarks and gluons.
124676188
Masses and Mass splittings of Charm mesons
Open charm hadrons with strange quark have been discovered in recent years but non-strange part have been somewhat ignored. We aim to calculate ground and excited low lying states charm meson masses using mass formulae developed in heavy hadron chiral perturbation theory. Also various parameters in one loop mass formulae are analyzed graphically within their respective ranges. We here provide the more constrained fits for different parameters. Spin and mass splittings are also calculated
72266124
Phenomenology of Neutrino Mixing in Vacuum and Matter
The current status and some perspectives of the phenomenology of massive neutrinos is reviewed. We start with the phenomenology of neutrino oscillations in vacuum and in matter. We summarize the results of neutrino experiments using solar, atmospheric. The fundamental theory of flavor changing neutrinos that has confirmed the neutrino oscillations and the various parameters affecting these oscillations have been discussed in detail. Specifically we will take the solar and atmospheric neutrino case. The oscillation plots will be discussed in detail, based on their behavior in vacuum and matter. Both normal and inverted mass hierarchy hypotheses are tested and both are consistent with observation. Finally the sensitivity of theta 13 over these probability oscillations has been analyzed and commented.
119303742
Strange and non-strange sea quark–gluon effects in nucleons
Abstract Within a statistical approach, strange and non-strange quark–gluon Fock state contributions are analyzed for their low energy properties. A suitable wave function is written for a nucleon that consists of three valence quarks ( qqq ) and the sea ( g , q q ¯ ). Expansion of the nucleonic system in terms of Fock states that contain ( g , q q ¯ ) is assumed and the probabilities of all possible Fock states, that lead to such a wave-function containing strange and non-strange quark–gluon contents in the sea are determined. Various approximations are entertained to validate the authenticity of the model used. The statistically determined coefficients strongly favor a vector-dominated sea where the sea includes s s ¯ pairs. Additionally, the sea is constrained to have a limited number of components. The phenomenological implications that affect the low energy properties are discussed. The obtained results are compared to existing theoretical models and experimental data.
118408611
Heavy quark effective theory for charmed mesons
Within the framework of heavy quark effective theory and chiral perturbation theory, masses and splittings of heavy charm mesons are studied. A mass formula is used for comprehensive analysis of low lying charm meson states.The variation of mass splittings and spin splittings with respect to various symmetry conserving and symmetry breaking parameters have also been focussed.
15233182
Phase velocity and particle injection in a self-modulated proton-driven plasma wakefield accelerator.
It is demonstrated that the performance of the self-modulated proton driver plasma wakefield accelerator is strongly affected by the reduced phase velocity of the plasma wave. Using analytical theory and particle-in-cell simulations, we show that the reduction is largest during the linear stage of self-modulation. As the instability nonlinearly saturates, the phase velocity approaches that of the driver. The deleterious effects of the wake's dynamics on the maximum energy gain of accelerated electrons can be avoided using side-injections of electrons, or by controlling the wake's phase velocity by smooth plasma density gradients.
54773207
Optimization of Nonlinear Wakefield Amplitude in Laser Plasma Interaction
Nonlinear, large amplitude, plasma waves are excited in the wake of an intense laser pulse propagating in a cold plasma, providing acceleration gradients ~ GeV/m. Linear analytic theory has shown that the wakefield amplitude is optimal for a certain ratio of the pulse length and plasma wavelength [1,2]. Here we present simulation studies to optimize the wake amplitude. The wake amplitude of a Gaussian pulse profile is maximized with respect to the laser pulse length. Using two dimensional simulations, it is seen that for a Gaussian pulse profile, the optimal pulse length derived from linear theory is also close to optimal (higher charge, smaller energy spread) for the generation of a quasi-monoenergetic electron beam in the bubble regime of laser plasma interaction. We also show, by varying the spot-size but keeping the intensity constant, that the magnitude of the trapped charge is a function primarily of the ratio P/Pc.
145031396
SIMULATION OF ELECTRON ACCELERATION BY TWO LASER PULSES PROPAGATING IN A HOMOGENOUS PLASMA
We study electron acceleration by two laser pulses copropagating one behind the other in a homogeneous plasma. We show, using one-dimensional simulations, that the wake amplitude can be amplified or diminished depending on the time delay between the two lasers, in agreement with linear analytic theory [1]. We extend the study to the bubble regime using two-dimensional simulations. We find that the one-dimensional optimization holds in two dimensions also. Trapping and acceleration of quasi-monoenergetic electrons (up to around 300 MeV) is found in the bucket behind the second laser, even for low intensities, where there is no trapping with a single laser. Thus, this scheme could be very useful for achieving a desired accelerated energy with less intense lasers, or, equivalently, increasing the accelerated energy for a given laser intensity.