Spin-distribution measurement: A sensitive probe for incomplete fusion dynamics
Spin distributions of various reaction products populated via complete and/or incomplete fusion of {sup 16}O with {sup 169}Tm have been measured at projectile energy {approx_equal}5.6 MeV/nucleon. Particle (Z=1,2) {gamma}-coincidences have been employed to achieve the information about involved reaction modes on the basis of their entry state spin populations. The experimentally measured spin distributions for incomplete fusion products have been found to be distinctly different than those observed for complete fusion products. The driving input angular momenta associated with incomplete fusion products have been found to be relatively higher than complete fusion products, and increases with direct {alpha}-multiplicity. It has also been observed that incomplete fusion products are less fed and/or the population of lower spin states are strongly hindered, while complete fusion products indicating strong feeding over a broad spin range.

title: Effect of entrance-channel parameters on incomplete fusion reactions
abstract: An attempt has been made to have exclusive information on effect of various entrance channel parameters on the onset of incomplete fusion in heavy ion induced reactions at energies at 4 7 MeV/A. A number of experiments have been performed by our group to measure the excitation function and forward recoil range distribution of various evaporation residues populated via complete fusion and/or incomplete fusion of O with different targets. The experimental excitation functions have been analysed in the frame work of compound nucleus decay using statistical model code PACE-4. Analysis of data suggests the existance of incomplete fusion even at energies as low as near barrier energies where complete fusion is supposed to be the sole contributor. Further more, in order to understand incomlete fusion reactions in a more conclusive way, the incomplete fusion fraction has been analyzed with the existing data for αcluster projectiles with different targets of low, medium and heavy mass region. The study of percentage incomplete fusion fraction for different projectile target combinations deduced from experimentally measured excitation functions of individual reaction product shows strong dependence on projectile energy, mass asymmetry of interacting partners and α−Q value of the projectile.

title: Preequilibrium emission in α induced reactions on bromine and thallium

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: 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: 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: PSEUDORAPIDITY DISTRIBUTION OF SHOWER PARTICLES IN 28Si-EMULSION INTERACTIONS AT 4.5 A GeV/c PER NUCLEON
abstract: Pseudorapidity density distributions of relativistic charged particles produced in 28Si-induced interactions in nuclear emulsion at JINR Synchrophasotron have been measured. The particle distributions in minimum-bias events exhibit a pronounced forward asymmetry with respect to the peak in the pseudorapidity spectra. The effect of intranuclear collisions on the mean pseudorapidity distribution versus the shower particles (ns) or the grey particles is discussed and compared with similar studies of 28Si and 32S at BNL AGS and CERN SPS energies respectively.

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.

title: Inclusive cross section and single transverse spin asymmetry for very forward neutron production in polarized p+p collisions at √s=200 GeV
abstract: The energy dependence of the single-transverse-spin asymmetry, A(N), and the cross section for neutron production at very forward angles were measured in the PHENIX experiment at the Relativistic Heavy Ion Collider for polarized p + p collisions at root s = 200 GeV. The neutrons were observed in forward detectors covering an angular range of up to 2.2 mrad. We report results for neutrons with a momentum fraction of x(F) = 0.45 to 1.0. The energy dependence of the measured cross sections were consistent with x(F) scaling, compared to measurements by an experiment at the Intersecting Storage Ring, which measured neutron production in unpolarized p + p collisions at root s = 30.6-62.7 GeV. The cross sections for large x(F) neutron production for p + p collisions, as well as those in e + p collisions measured at the Hadron-Electron Ring Accelerator, are described by a pion exchange mechanism. The observed forward neutron asymmetries were large, reaching A(N) = -0.08 +/- 0.02 for x(F) = 0.8; the measured backward asymmetries, for negative x(F), were consistent with zero. The observed asymmetry for forward neutron production is discussed within the pion exchange framework, with interference between the spin-flip amplitude due to the pion exchange and nonflip amplitudes from all Reggeon exchanges. Within the pion exchange description, the measured neutron asymmetry is sensitive to the contribution of other Reggeon exchanges even for small amplitudes.

title: Transition in yield and azimuthal shape modification in dihadron correlations in relativistic heavy ion collisions.
abstract: Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of π^{0} trigger particles at transverse momenta p{T}{t}=4-12  GeV/c and associated charged hadrons (p{T}{a}=0.5-7  GeV/c) vs relative azimuthal angle Δϕ in Au+Au and p+p collisions at sqrt[s{NN}]=200  GeV. The Au+Au distribution at low p{T}{a}, whose shape has been interpreted as a medium effect, is modified for p{T}{t}<7  GeV/c. At higher p{T}{t}, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p{T}{a}, which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au+Au relative to p+p (I{AA}) is suppressed at high p{T} (I{AA}≈0.35-0.5), but less than for inclusive suppression (R{AA}≈0.2).