arXiv subjects

V. Jha

Publications and source records attributed to V. Jha.

29 records · Page 2Linked to original sources

arXiv2018

A plastic scintillator array for reactor based anti-neutrino studies

Indian Scintillator Matrix for Reactor Anti-Neutrinos (ISMRAN), a plastic scintillator array (10$\times$10), is being constructed for the purpose of electron anti-neutrino ($\overline\nuup_{e}$) detection for reactor monitoring applications. A prototype detector called mini-ISMRAN, which consists of 16$\%$ of ISMRAN, has been setup for studying the detector response, background rates and event characterization in the reactor and non-reactor environment. The data acquisition system based on waveform digitizers is being used for pulse processing and event triggering. Monte-Carlo based simulations using GEANT4 are performed to optimize lead (Pb) and borated polyethylene (BP) shielding for background reduction and to study the positron, neutron and $γ$-ray response in the ISMRAN detector. Characterization of plastic scintillator detectors with known radioactive sources is done for energy, timing and position measurements. Using the energy summation and bar multiplicity selection, coincident events from $\mathrm{{}^{60}Co}$ decay are reconstructed in non-reactor environment. Results from background measurements using various detectors are quantified in reactor ON and OFF condition. The shielding of 10 cm Pb and 10 cm BP along with the requirement of hits in multiple bars, reduces the uncorrelated background in reactor ON condition.

physics.ins-det↗

arXiv2018

Deep-inelastic multinucleon transfer processes in the $^{16}$O+$^{27}$Al reaction

The reaction mechanism of deep-inelastic multinucleon transfer processes in the $^{16}$O+$^{27}$Al reaction at an incident $^{16}$O energy ($E_{\rm lab}=134$ MeV) substantially above the Coulomb barrier has been studied both experimentally and theoretically. Elastic-scattering angular distribution, total kinetic energy loss spectra and angular distributions for various transfer channels have been measured. The $Q$-value- and angle-integrated isotope production cross sections have been deduced. To obtain deeper insight into the underlying reaction mechanism, we have carried out a detailed analysis based on the time-dependent Hartree-Fock (TDHF) theory. A recently developed method, TDHF+GEMINI, has been applied to evaluate production cross sections for secondary products. From a comparison between the experimental and theoretical cross sections, we find that the theory qualitatively reproduces the experimental data. Significant effects of secondary light-particle emissions are demonstrated. Possible interplay between fusion-fission, deep-inelastic, multinucleon transfer and particle evaporation processes are discussed.

nucl-ex↗

arXiv2018

Investigation of complete and incomplete fusion in $^{7}$Li+$^{124}$Sn reaction around Coulomb barrier energies

The complete and incomplete fusion cross sections for $^{7}$Li+$^{124}$Sn reaction were measured using online and offline characteristic $γ$-ray detection techniques. The complete fusion (CF) cross sections at energies above the Coulomb barrier were found to be suppressed by $\sim$ 26 \% compared to the coupled channel calculations. This suppression observed in complete fusion cross sections is found to be commensurate with the measured total incomplete fusion (ICF) cross sections. There is a distinct feature observed in the ICF cross sections, i.e., $\textit{t}$-capture is found to be dominant than $α$-capture at all the measured energies. A simultaneous explanation of complete, incomplete and total fusion (TF) data was also obtained from the calculations based on Continuum Discretized Coupled Channel method with short range imaginary potentials. The cross section ratios of CF/TF and ICF/TF obtained from the data as well as the calculations showed the dominance of ICF at below barrier energies and CF at above barrier energies.

nucl-ex↗

arXiv2016

Exploring contributions from incomplete fusion in $^{6,7}$Li+$^{209}$Bi and $^{6,7}$Li+$^{198}$Pt reactions

We use the breakup absorption model to simultaneously describe the measured cross-sections of the Complete fusion (CF), Incomplete fusion (ICF), and Total fusion (TF) in nuclear reactions induced by weakly bound nuclei $^{6,7}$Li on $^{209}$Bi and $^{198}$Pt targets. The absorption cross-sections are calculated using the Continuum Discretized Coupled Channels (CDCC) method with different choices of short range imaginary potentials to get the ICF, CF and TF cross-sections. It is observed that the cross-sections for deuteron-ICF/deuteron-capture are of similar magnitude as the $α$-ICF/$α$-capture, in case of $^{6}$Li projectile, while the cross-sections for triton-ICF/triton-capture is more dominant than $α$-ICF/$α$-capture in case of $^{7}$Li projectile. Both these observations are also corroborated by the experimental data. The ratio of ICF to TF cross-sections, which defines the value of fusion suppression factor is found to be in agreement with the data available from the literature. The cross-section ratio of CF/TF and ICF/TF show opposite behavior, the former decreases while the latter increases as the energy is lowered, which shows the dominance of ICF at below barrier energies. We have also studied the correlation of the ICF cross-sections with the non-capture breakup (NCBU) cross-sections as a function of energy, which shows that the NCBU is more significant than ICF at below barrier energies.

nucl-th↗

arXiv2014

Understanding fusion and its suppression for the $^{9}$Be projectile with different targets

The role of the breakup process and one neutron stripping on the near barrier fusion are investigated for the weakly bound projectile $^{9}$Be on $^{28}$Si, $^{89}$Y, $^{124}$Sn, $^{144}$Sm and $^{208}$Pb targets. Continuum-discretized coupled channels (CDCC) calculations for the breakup with a $^{8}$Be + n model of the $^{9}$Be nucleus and coupled reactions channels (CRC) calculations for the one neutron stripping to several single particle states in the target are performed for these systems. A good description of the experimental fusion cross sections above the Coulomb barrier is obtained from the CDCC-CRC calculations for all the systems. The calculated incomplete fusion probabilities for different target systems are found to be consistent with the systematic behaviour of the complete fusion suppression factors as a function of target atomic mass, obtained from the experimental data.

nucl-ex↗

arXiv2013

Exploring the breakup and transfer coupling effects in 9Be elastic scattering

Two cluster structures of 9Be namely, 5He+4He and 8Be+n have been considered for its breakup to describe the available data on elastic scattering for 9Be projectile with 28Si, 64Zn and 144Sm targets. The results of these calculations suggest that the breakup coupling effects are significant for 5He+4He cluster model at above the barrier energies, while they are dominant at relatively lower energies for 8Be+n model. The addition of one neutron stripping channel in the 8Be+n model gives an overall good description of the elastic data for all the systems considered. The couplings generated by breakup in 8Be+n model have different behaviour than the coupling effects obtained within the 5He+4He model, the former being more prominent at lower energies and for the heavier target systems. The behaviour of extracted dynamic polarisation potentials (DPP) generated due to breakup and one neutron transfer couplings have been investigated.

nucl-th↗

arXiv2010

Study of the $\bm{p+^6}$Li$\bm{\toη+^7}$Be reaction 11.3 MeV above threshold

The cross section for the reaction $p+^6\text{Li}\toη+^7\text{Be}$ was measured at an excess energy of 11.28 MeV above threshold by detecting the recoiling $^7$Be nuclei. A dedicated set of focal plane detectors was built for the magnetic spectrograph Big Karl and was used for identification and four momentum measurement of the $^7$Be. A differential cross section of $\frac{dσ}{dΩ}=(0.69\pm{0.20}\text{(stat.)}\pm 0.20\text{(syst.)})\text{nb/sr}$ for the ground state plus the 1/2$^-$ was measured. The result is compared to model calculations.

nucl-ex↗

arXiv2009

Precision measurements of the pp\to π^+pn and pp\to π^+d reactions: importance of long-range and tensor force effects

Inclusive measurements of pion production in proton--proton collisions in the forward direction were undertaken at 400 and 600 MeV at COSY using the Big Karl spectrograph. The high resolution in the $π^+$ momentum ensured that there was an unambiguous separation of the $pp\to π^+d/π^+pn$ channels. Using these and earlier data, the ratio of the production cross sections could be followed through the $Δ$ region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final $pn$ system. These have been investigated in a realistic $pp\toπ^+d/π^+pn$ calculation that includes $S \rightleftharpoons D$ channel coupling between the final nucleons. A semi-quantitative understanding of the observed effects is achieved.

nucl-ex↗

arXiv2008

Cross Section and Tensor Analysing Power of the $\vec{d}d\to ηα$ Reaction Near Threshold

The angular distributions of the unpolarised differential cross section and tensor analysing power $A_{xx}$ of the $\vec{d}d\toαη$ reaction have been measured at an excess energy of 16.6 MeV. The ambiguities in the partial-wave description of these data are made explicit by using the invariant amplitude decomposition. This allows the magnitude of the s-wave amplitude to be extracted and compared with results published at lower energies. In this way, firmer bounds could be obtained on the scattering length of the $ηα$ system. The results do not, however, unambiguously prove the existence of a quasi-bound $ηα$ state.

nucl-ex↗

arXiv2005

Measurement of the Vector and Tensor Polarisation of Proton and Deuteron Beams

Measurement of the d + d -> 4He + eta reaction using vector and tensor polarised beam has been performed at COSY using Big Karl magnetic spectrograph. The beam polarisation necessary for obtaining the vector and tensor analysing power for this reaction was measured. The method and the results of the tensor polarisation measurement of the deuteron beam are presented.

hep-ex↗

arXiv2005

A precision determination of the mass of the $η$ meson

Several processes of meson production in proton-deuteron collisions have been measured simultaneously using a calibrated magnetic spectrograph. Among these processes, the $η$ meson is seen clearly as a sharp missing--mass peak on a slowly varying background in the $p+d\to ^3\textrm{He} +X$ reaction. Knowing the kinematics of the other reactions with well determined masses, it is possible to deduce a precise mass for the $η$ meson. The final result, $m(η)=547.311\pm 0.028 \textrm{(stat)} \pm 0.032 \textrm{(syst) MeV/c}^2$, is significantly lower than that found by the recent NA48 measurement, though it is consistent with values obtained in earlier counter experiments.

hep-ex↗