118407421
Observation of direct-photon collective flow in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions
The second Fourier component v_2 of the azimuthal anisotropy with respect to the reaction plane was measured for direct photons at midrapidity and transverse momentum (p_T) of 1--13 GeV/c in Au+Au collisions at sqr(s_NN)=200 GeV. Previous measurements of this quantity for hadrons with p_T 6 GeV/c a reduced anisotropy is interpreted in terms of a path-length dependence for parton energy loss. In this measurement with the PHENIX detector at the Relativistic Heavy Ion Collider we find that for p_T > 4 GeV/c the anisotropy for direct photons is consistent with zero, as expected if the dominant source of direct photons is initial hard scattering. However, in the p_T < 4 GeV/c region dominated by thermal photons, we find a substantial direct photon v_2 comparable to that of hadrons, whereas model calculations for thermal photons in this kinematic region significantly underpredict the observed v_2.
54934681
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.
120964131
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.
121122740
PSEUDORAPIDITY DISTRIBUTION OF SHOWER PARTICLES IN 28Si-EMULSION INTERACTIONS AT 4.5 A GeV/c PER NUCLEON
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.
60626146
ILC Reference Design Report: ILC Global Design Effort and World Wide Study
122669680
Charged Particles Multiplicity in Interactions of 3.7 A GeV 28Si with Light and Heavy Target Nuclei in Nuclear Emulsions
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.
120744347
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.
122406045
Preequilibrium emission in α induced reactions on bromine and thallium
123908854
Effect of entrance-channel parameters on incomplete fusion reactions
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.
120483275
Role of high ℓ values in the onset of incomplete fusion
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 $^{16}\mathrm{O}({E}_{\mathrm{lab}}\ensuremath{\approx}5.6A \mathrm{MeV}) + ^{169}\mathrm{Tm}$ 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.