arXiv subjects

D. P. Mahapatra

Publications and source records attributed to D. P. Mahapatra.

22 records · Page 2Linked to original sources

arXiv1999

Localized Domains of Disoriented Chiral Condensates

A new method to search for localized domains of disoriented chiral condensates (DCC) has been proposed by utilising the (eta-phi) phase space distributions of charged particles and photons. Using the discrete wavelet transformation (DWT) analysis technique, it has been found that the presence of DCC domains broadens the distribution of wavelet coefficients in comparison to that of normal events. Strength contours have been derived from the differences in rms deviations of these distributions by taking into account the size of DCC domains and the probability of DCC production in ultra-relativistic heavy ion collisions. This technique can be suitably adopted to experiments measuring multiplicities of charged particles and photons.

nucl-ex↗

arXiv1998

Search for DCC in Relativistic Heavy-Ion Collision Through Event Shape Analysis

Event shape analysis has been used to look for DCC signals in simulated ultra-relativistic heavy-ion collision data at SPS energy. A simple redistribution of particles, with two detectors to detect charged particles and photons, is seen to result in the same flow direction with the flow angle difference peaking at zero. However, events where the neutral pion fraction has been modified according to the DCC probability distribution, show the flow angles in two detectors to be almost $90^o$ apart. The results presented here show that the technique is complementary to the one based on the discrete wavelet transformation. Together the techniques are seen to provide a very powerful tool for DCC search in ultra relativistic heavy ion collision.

nucl-ex↗

arXiv1998

A Preshower Photon Multiplicity Detector for the WA98 Experiment

A high granularity preshower detector has been fabricated and installed in the WA98 Experiment at the CERN SPS for measuring the spatial distribution of photons produced in the forward region in lead ion induced interactions. Photons are counted by detecting the preshower signal in plastic scintillator pads placed behind a 3 radiation length thick lead converter and applying a threshold on the scintillator signal to reject the minimum ionizing particles. Techniques to improve the imaging of the fibre and performance of the detector in the high multiplicity environment of lead-lead collisions are described. Using Monte-Carlo simulation methods and test beam data of pi- and e- at various energies the photon counting efficiency is estimated to be 68% for central and 73% for peripheral Pb+Pb collisions.

hep-ex↗

arXiv1994

Shape Transition in the Epitaxial Growth of Gold Silicide in Au Thin Films on Si(111)

Growth of epitaxial gold silicide islands on bromine-passivated Si(111) substrates has been studied by optical and electron microscopy, electron probe micro analysis and helium ion backscattering. The islands grow in the shape of equilateral triangles up to a critical size beyond which the symmetry of the structure is broken, resulting in a shape transition from triangle to trapezoid. The island edges are aligned along $Si[110]$ directions. We have observed elongated islands with aspect ratios as large as 8:1. These islands, instead of growing along three equivalent [110] directions on the Si(111) substrate, grow only along one preferential direction. This has been attributed to the vicinality of the substrate surface.

cond-mat↗