Cross section and double helicity asymmetry for eta mesons and their comparison to neutral pion production in p+p collisions at sqrt(s)=200 GeV
Measurements of double-helicity asymmetries in inclusive hadron production in polarized p+p collisions are sensitive to helicity-dependent parton distribution functions, in particular to the gluon helicity distribution, {Delta}g. This study focuses on the extraction of hte double-helicity asymmetry in {eta} production (p+p{yields}{eta}+X), the {eta} cross section, and the {eta}/{pi}{sup 0} cross section ratio. The cross section and ratio measurements provide essential input for the extraction of fragmentation functions that are needed to acess the helicity-dependent parton distribution functions.

title: Prediction of Charged Hadron Multiplicity at LHC and CBM Experiments
abstract: A systematic study of charged hadron multiplicities ($n_{ch}$) at various collision energies is very much important in understanding the basic production mechanism of the hadrons in nucleus-nucleus collision experiments. Furthermore, the variations of $n_{ch}$ in nucleus-nucleus collisions with respect to the colliding energy and mass number can provide a potential probe for the formation of quark gluon plasma (QGP) in the laboratory. In this paper, we propose a phenomenological model based on the constituent quark-quark interactions to calculate the average multiplicity ($n_{ch}$) and pseudorapidity density at mid-rapidity ($(dn_{ch}/d\eta)_{\eta=0}$) of charged hadrons at various center-of-mass energies $(\sqrt{s_{NN}})$ for nucleus-nucleus ($A-A$) collisions. We first propose a new parametrization for $n_{ch}^{pp}$ and $(dn_{ch}/d\eta)^{pp}_{\eta=0}$ in $p-p$ interactions based on some initial inputs which fit the experimental data very well. We further extend this parametrization by using simple phenomenological assumptions regarding mean number of participating quarks and mean number of collisions to obtain the $n_{ch}$ and $(dn_{ch}/d\eta)_{\eta=0}$ for $A-A$ collisions and show their dependencies on the mass number of colliding nuclei as well as on $\sqrt{s_{NN}}$. We also compare the results obtained from our model with the results obtained from the modified Glauber model in order to demonstrate the difference between the two formalisms. Finally, we compare the charged hadron multiplicity and pseudorapidity density at mid-rapidity for $A-A$ collisions obtained from our model with the available experimetal data from various heavy-ion collision experiments and give our predictions for $A-A$ collisions at the Large Hadron Collider (LHC) and at Compressed Baryonic Matter (CBM) experiments.

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: 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: Charged Particles Multiplicity in Interactions of 3.7 A GeV 28Si with Light and Heavy Target Nuclei in Nuclear Emulsions
abstract: Results from measurement of multiplicity of different charged particles emitted from the interactions of 3.7 A GeV 28 Si with different target groups in nuclear emulsion and correlations among them are presented. The nature of the dependence of multiplicities of charged particles on the impact parameter is examined. Analysis of data in terms of specific multiplicity for different target groups is performed and the results are discussed in the light of superposition model.

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).

title: Reaction mechanism in the O 16 + Al 27 system: Measurements and analysis of excitation functions and angular distributions
abstract: To study the dynamics of heavy ion fusion reactions in the lower mass region, experiments were carried out to measure the cross sections of radioactive residues produced in the interaction of the {sup 16}O ion with {sup 27}Al target nucleus at 19 different energies in very close intervals covering the energy range from {approx_equal}58 to 94 MeV, using the well-known recoil catcher off-line {gamma}-ray spectroscopy technique. The simulation of experimental data was performed using statistical-model-based computer codes, viz., CASCADE, PACE2, and ALICE-91. The analysis of measured excitation functions indicates that these residues are likely to be produced by complete fusion, incomplete fusion, and direct reaction processes. Furthermore, to confirm the contribution of different reaction channels, a complementary experiment was performed that measured the angular distributions of the residues produced in the {sup 16}O+{sup 27}Al system at 85 MeV beam energy. The analysis of the results of both experiments indicates that at these energies, the direct reactions compete with complete fusion and incomplete fusion reaction processes.

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: 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: Incomplete fusion dynamics by spin distribution measurements
abstract: Spin distributions for various evaporation residues populated via complete and incomplete fusion of $^{16}\mathrm{O}$ with $^{124}\mathrm{Sn}$ at $6.3$ MeV/nucleon have been measured, using charged particles ($Z=1,2$)-$\ensuremath{\gamma}$ coincidence technique. Experimentally measured spin distributions of the residues produced as incomplete fusion products associated with ``fast'' $\ensuremath{\alpha}$- and $2\ensuremath{\alpha}$-emission channels observed in the ``forward cone'' are found to be distinctly different from those of the residues produced as complete fusion products. Moreover, ``fast'' $\ensuremath{\alpha}$-particles that arise from larger angular momentum in the entrance channel are populated at relatively higher driving input angular momentum than those produced through complete fusion. The incomplete fusion residues are populated in a limited, higher-angular-momentum range, in contrast to the complete fusion products, which are populated over a broad spin range.