Preequilibrium emission in α induced reactions on bromine and thallium

title: Complete and incomplete fusion of 12 C with 165 Ho below 7 MeV/nucleon: Measurements and analysis of excitation functions
abstract: This experiment has been done with a view to studying complete and incomplete fusion in heavy-ion-induced reactions. Excitation functions for several reactions induced by ${}^{12}{\mathrm{C}}^{5+}$ ions on ${}^{165}\mathrm{Ho}$ at incident energies from 55 to 80 MeV have been measured using the activation technique. The analysis of the data has been done using the codes ALICE-91 and CASCADE. The parameter ${F}_{\ensuremath{\theta}},$ the ratio of actual moment of inertia to the rigid-body value, has been found to play an important role in the calculations done by the code CASCADE. Significant contributions from both the complete and the incomplete fusion channels have been observed. Further, in the case of the reaction $(\mathrm{C},p3n)$ considerable contribution from the decay of higher charge isobar precursor has been observed.

title: Equilibrium and preequilibrium emission in some alpha -induced reactions on enriched isotopes 128,130Te at moderate excitation energies.
abstract: Excitaion functions for the reactions [sup 128]Te([alpha],[ital np])[sup 130]I, [sup 130]Te([alpha],[ital np])[sup 132]I, and [sup 130]Te([alpha],[ital np])[sup 132[ital m]]I have been measured using the stacked foil technique and have also been calculated using a statistical model with and without the inclusion of preequilibrium emission. As expected, the inclusion of preequilibrium emission in compound nucleus calculations agrees well with the experimental excitation functions. The preequilibrum fraction has been found to be energy and target mass number dependent.

title: Role of high ℓ values in the onset of incomplete fusion
abstract: A particle-$\ensuremath{\gamma}$-coincidence experiment is performed to investigate the role of high $\ensuremath{\ell}$ values in the production of direct-$\ensuremath{\alpha}$-emitting channels (associated with incomplete fusion) in $^{12}\mathrm{C}+^{169}\mathrm{Tm}$ system. Spin distributions of various $\mathit{xn}/\mathit{pxn}/\ensuremath{\alpha}\mathit{xn}/2\ensuremath{\alpha}\mathit{xn}$ channels are measured at ${E}_{\mathrm{lab}}=5.6A$ and $6.5A$ MeV. Entirely different de-excitation patterns are observed in direct-$\ensuremath{\alpha}$-emitting channels and fusion-evaporation channels. The fusion-evaporation channels are found to be strongly fed over a broad spin range. While narrow range feeding for only high-spin states was observed in the case of direct-$\ensuremath{\alpha}$-emitting channels, in the present work, incomplete fusion is shown to be a promising tool to populate high-spin states in final reaction products. To have better insight into the associated $\ensuremath{\ell}$ values in different reaction channels, the present data are compared with similar data obtained in $^{16}\mathrm{O}({E}_{\mathrm{lab}}\ensuremath{\approx}5.6A \mathrm{MeV}) +  system. The mean driving angular momenta involved in the production of direct-$\ensuremath{\alpha}$-emitting channels are found to be higher than those involved in the production of fusion-evaporation channels. Direct-$\ensuremath{\alpha}$ multiplicity in the forward cone increases with driving angular momenta, which indicates the origin of direct-$\ensuremath{\alpha}$-emitting channels at high $\ensuremath{\ell}$ values in noncentral interactions.

title: Integral frequency distribution of projectile alpha fragments in nuclear multifragmentations at intermediate and high energies
abstract: The integral frequency distributions of the numbers of projectile alpha fragments produced in nuclear multifragmentations at intermediate and high energies are studied by a simple two-source model. The calculated results are approximately in agreement with the experimental data of 16 O, 40 Ar, 56 Fe, 84 Kr, 139 La, and 197 Au multifragmentations in nuclear emulsions at 2.00 A , 1.80 A , 1.80 A , 0.08–1.70 A , 0.60–0.99 A , and 0.60–0.99 A GeV, respectively. The initial energy of nuclear limiting fragmentation is expected to be at or lower than 0.08 A GeV. Two correlations between the mean multiplicity of projectile alpha fragments ( 〈 n α 〉 ) and the projectile mass number, as well as 〈 n α 〉 and the maximum multiplicity of projectile alpha fragments are observed.

title: Some general properties of projectile fragments in 40Ar interactions in nuclear emulsions at 1.8 A GeV
abstract: An analysis of projectile fragments has been performed using 40Ar-emulsion interactions at 1.8 A GeV. The interaction mean free path of 40Ar nuclei was obtained on the basis of 4600 events which enabled one to calculate the total inelastic cross section. Correlations between the multiplicity of different charged particles were studied extensively to get an insight into the reaction mechanism. The average number of interacting nucleons of the projectile was calculated and compared with results from other experiments. Events with projectile fragments were divided into various reaction channels and several parameters like average emission angle and target particle multiplicities were studied as a function of target mass in different reaction channels. The projectile fragmentation properties were found to be independent of the target for peripheral collisions.

title: Cross sections and double-helicity asymmetries of midrapidity inclusive charged hadrons in p+ p collisions at sqrt (s)= 62.4 GeV
abstract: Unpolarized cross sections and double-helicity asymmetries of single-inclusive positive and negative charged hadrons at midrapidity from p + p collisions at root s = 62.4 GeV are presented. The PHENIX measurement of the cross sections for 1.0 < p(T) < 4.5 GeV/c are consistent with perturbative QCD calculations at next-to-leading order in the strong-coupling constant, alpha(s). Resummed pQCD calculations including terms with next-to-leading-log accuracy, yielding reduced theoretical uncertainties, also agree with the data. The double-helicity asymmetry, sensitive at leading order to the gluon polarization in a momentum-fraction range of 0.05 less than or similar to x(gluon) less than or similar to 0.2, is consistent with recent global parametrizations disfavoring large gluon polarization.

title: Ageing of CsI thin film photocathodes induced by UV photons
abstract: The degradation of CsI thin film photocathodes (PCs) under UltraViolet (UV) irradiation has been investigated by measuring the photocurrent as well as the absolute Quantum Efficiency (QE) as a function of the accumulated charge density. Atomic Force Microscopy (AFM) and UV Photoemission Electron Microscopy (PEEM) have been employed to study the surface morphology and the local QE of polycrystalline CsI thin films and their transformation due to UV irradiation. The photoemissive properties of CsI PCs, together with their surface morphology, have been found to be strongly affected by the UV photon ageing.

title: Study of Projectile Helium (Z = 2) Fragments Produced in Nucleus–Nucleus Interactions at 14.6 A GeV
abstract: An analysis of projectile helium ( Z = 2) fragments emitted from 855 minimum-bias events of 28 Si projectiles in nuclear emulsion at 14.6 A GeV has been performed. An event-by-event examination has been made from the minimum-bias events in order to see the dependence of shower and target fragments multiplicities in individual helium reaction channels. The validity of KNO scaling for the projectile helium ( Z = 2) fragments has also been studied. The angular and derived pseudorapidity and momentum distributions of projectile helium ( Z = 2) fragments are found to be characteristically Gaussian shaped with some width σ.