Searcharxiv⌕ Search

arXiv subjects

Mahnaz Q. Haseeb

Publications and source records attributed to Mahnaz Q. Haseeb.

16 recordsLinked to original sources
arXiv2013

Second order photon loops at finite temperature and charge renormalization

We present two loop corrections to photon self energy at finite temperature in real time formalism. An expression for renormalized coupling constant has been derived in a form that is relevant for all temperature ranges of interest in QED, specifically for temperatures around T \sim m, where m is electron mass. Temperature dependence is mainly contributed by hot fermions at T \ge m. We use the calculations of vacuum polarization to determine the dynamically generated mass of photon, Debye screening length, plasma frequency up to the second order in αas well as the electromagnetic properties of a medium at m \le T \le 2m temperature. For higher temperatures, the existing renormalization scheme does not work well because of the increase in coupling constant. To exactly determine the validity of renormalization scheme, higher order calculations are required. The temperature T \sim m is of specific interest from the point of view of the early universe. Such calculations have acquired more significance recently due to the possibility of producing electron-positron plasmas in laboratory.

hep-th↗
arXiv2013

Primordial Nucleosynthesis and Finite Temperature QED

Abundances of light nuclei formed during primordial nucleosynthesis are predicted by Standard Big Bang Model. The latest data from WMAP, with precision's higher than ever before, provides a motivation to determine theoretical higher order corrections to change in helium abundance and the related parameters. Here we evaluate the QED corrections to the change in these parameters during primordial nucleosynthesis using finite temperature effects at the two loop level. Relative variations in neutron decay rate, total energy density of the universe, relative change in neutrino temperature etc., with two loop corrections to electron mass, at the timescale when QED corrections were relevant, have been estimated.

astro-ph.CO↗
arXiv2013

Second Order Corrections to the Magnetic Moment of Electron at Finite Temperature

Magnetic moment of electron at finite temperature is directly related to the modified electron mass in the background heat bath. Magnetic moment of electron gets modified when it couples with the magnetic field at finite temperature through its temperature dependent physical mass. We show that the magnetic moment of electron becomes a complicated function of temperature and even change its temperature dependent behavior around the energies for primordial nucleosynthesis. We calculate the self-mass induced thermal contributions to the magnetic moment of electron, up to the two loop level, for temperatures valid around the era of primordial nucleosynthesis. A comparison of thermal behavior of the magnetic moment is also quantitatively studied in detail, around the temperatures below and above nucleosynthesis temperature range.

hep-th↗
arXiv2011

Second Order Thermal Corrections to Electron Wavefunction

Second order perturbative corrections to electron wavefunction are calculated here at generalized temperature, for the first time. This calculation is important to prove the renormalizeability of QED through order by order cancellation of singularities at higher order. This renormalized wavefunction could be used to calculate the particle processes in the extremely hot systems such as the very early universe and the stellar cores. We have to re-write the second order thermal correction to electron mass in a convenient way to be able to calculate the wavefunction renormalization constant. A procedure for integrations of hot loop momenta before the cold loop momenta integration is maintained throughout to be able to remove hot singularities in an appropriate way. Our results, not only includes the intermediate temperatures T m (where m is the electron mass), the limits of high temperature T>>m and low temperature T<<m are also retrievable. A comparison is also done with the existing results.

hep-ph↗
arXiv2011

Two Loop Low Temperature Corrections to Electron Self Energy

We recalculate the two loop corrections in the background heat bath using real time formalism. The procedure of the integrations of loop momenta with dependence on finite temperature before the momenta without it, has been followed. We determine the mass and wavefunction renormalization constants in the low temperature limit of QED, for the first time with this preferred order of integrations. The correction to electron mass and spinors in this limit is important in the early universe at the time of primordial nucleosynthesis as well as in astrophysics.

hep-ph↗
arXiv2009

Comparison of experimental and theoretical results to define centrality of heavy ion collisions

Using the simulation data coming from the cascade model, we have studied the behavior of event number as a function of impact parameter-b and a number of all charged particles- Nch for light and heavy nuclei at different energies. We have seen that for light nuclei, a number of all charged particles-Nch could be used to fix the centrality. But for heavy nuclei we have got strong initial energy and mass dependences and the results for impact parameter factor dependences and ones for a number of all charged particles differ. So for heavy nuclei, a number of charged particles-Nch could not be use to fix the centrality. Key words: cascade model; centrality, light nuclei, heavy nuclei

nucl-ex↗
arXiv2009

Some properties of the central heavy ion collisions

Some experimental results are discussed in connection with the properties of the central heavy ion collisions. These experiments indicate the regime changes and saturation at some values of the centrality. This phenomenon is considered to be a signal of the percolation cluster formation in heavy ion collisions at high energies. Keywords: heavy ion collisions, theoretical models, centrality, phase transition.

nucl-ex↗
arXiv2009

Light nuclei production in heavy ion collisions

Light nuclei production as a result of nuclear coalescence effect can give some signals on final state of Quark Gluon Plasma formation. We are studying the behavior of nuclear modification factor as a function of different variables using the simulated data coming from the FASTMC generator. This data is necessary to extract information on coalescence mechanism from experimental data on high energy nuclear-nuclear interactions.

nucl-ex↗
arXiv2009

Some Properties of the Central pi--Meson Carbon Interactions at 40 Gev/C

We discuss some properties of the central pi--meson carbon reactions at 40 GeV/c. While these results were obtained many years ago they have not been explained completely. We attempt to interpret following: results regime change on the behavior of some characteristics of the events as a function of the centrality; anomaly peak on the angular distributions of the slow protons emitted in these reactions; charge asymmetry on the pi--mesons production in the back hemisphere in lcs. Understanding of the results could help to explain the new ones coming from the modern central experiments at high and ultrarelativistic energies.

hep-ex↗
arXiv2008

Second Order Corrections to QED Coupling at Low Temperature

We calculate the second order corrections to vacuum polarization tensor of photons at low temperatures, i.e; T $\le 10^{10}$ K ($T << m_e$). The thermal contributions to the QED coupling constant are evaluated at temperatures below the electron mass that is $T< m_e$ . Renormalization of QED at these temperatures has explicitly been checked. The electromagnetic properties of such a thermal medium are modified. Parameters like electric permittivity and magnetic permeability of such a medium are no more constant and become functions of temperature.

hep-ph↗
arXiv2007

Formation of the intermediate baryon systems in hadron-nuclear and nuclear-nuclear interactions

The centrality experiments indicate regime change and saturation in the behavior of some characteristics of the secondary particles emitted in hadron-nuclear and nuclear-nuclear interactions at high energies. The phenomenon has a critical character. The simple models do not explain the effect. We suppose that the responsible mechanism to explain the phenomenon could be the formation and decay of the intermediate baryon systems. Such systems could be formed as a result of nucleon percolation in compressed baryonic matter. Formation of big percolation cluster may change the properties of the medium, e.g., it could lead to the changing its transparency. This could be used to get a signal of the intermediate baryonic system formation. We consider two signals to identify the formation of the intermediate baryon systems: the critical changing of transparency of the strongly interacting matter and the enhancement of light nuclei production with increase in centrality.

nucl-ex↗
arXiv2007

Multiplicity and angular distribution of particles emitted in relativistic nuclear-nuclear interactions

We discuss the experimental results on the behavior of the average multiplicities and angular distributions of slow particles emitted in hadron-nuclear and nuclear-nuclear interactions at relativistic energies as a function of the centrality of collisions. It is observed that by increasing the mass of the projectiles the angular distributions of slow particles change and the structure which was demonstrated in the case of pi-mesons, protons and light nuclear projectiles, almost disappears. During the interaction of the heavier projectile with nuclear target, the number of secondary interactions as well as number of nucleon-nucleon elastic scattering and re-scattering events increases. We suggest to restore this information using the heavy ion generators taking into account the multiplicity distributions. Because our investigations show that the formation of the percolation cluster sufficiently influences the behaviour of the average multiplicity of the slow particles emitted in these interactions.

nucl-ex↗
arXiv2007

Search for deconfinement in the cluster at ultrarelativistic heavy ion collisions

Some of the centrality experiments indicate regime change and saturation in the behavior of characteristics of the secondary particles. It is observed as a critical phenomenon for hadron-nuclear, nuclear-nuclear interactions and ultrarelativistic heavy ion collisions. The existing simple models do not explain the effect. We believe that the responsible mechanism to explain the phenomena could be the percolation cluster formation and expect appearance of deconfinement in the cluster.

nucl-ex↗