A. Adare, S. Afanasiev, C. Aidala, N.N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander, K. Aok... more A. Adare, S. Afanasiev, C. Aidala, N.N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander, K. Aoki, Y. Aramaki, E. T. Atomssa, R. Averbeck, T. C. Awes, B. Azmoun, V. Babintsev, M. Bai, G. Baksay, L. Baksay, K. N. Barish, B. Bassalleck, A. T. Basye, S. Bathe, V. Baublis, C. Baumann, A. Bazilevsky, S. Belikov,* R. Belmont, R. Bennett, A. Berdnikov, Y. Berdnikov, A.A. Bickley, J. S. Bok, K. Boyle, M. L. Brooks, H. Buesching, V. Bumazhnov, G. Bunce, S. Butsyk, C.M. Camacho, S. Campbell, C.-H. Chen, C. Y. Chi, M. Chiu, I. J. Choi, R.K. Choudhury, P. Christiansen, T. Chujo, P. Chung, O. Chvala, V. Cianciolo, Z. Citron, B. A. Cole, M. Connors, P. Constantin, M. Csanád, T. Csörgő, T. Dahms, S. Dairaku, I. Danchev, K. Das, A. Datta, G. David, A. Denisov, A. Deshpande, E. J. Desmond, O. Dietzsch, A. Dion, M. Donadelli, O. Drapier, A. Drees, K.A. Drees, J.M. Durham, A. Durum, D. Dutta, S. Edwards, Y. V. Efremenko, F. Ellinghaus, T. Engelmore, A. Enokizono, H. En’yo, S. Esumi, B. Fadem, D. E. F...
During 2015, the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polar... more During 2015, the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized p+p collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in p+p collisions predicts only a moderate atomic-mass-number (A) dependence. In contrast, the asymmetries observed at RHIC in p+A collisions showed a surprisingly strong A dependence in inclusive forward neutron production. The observed asymmetry in p+Al collisions is much smaller, while the asymmetry in p+Au collisions is a factor of 3 larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed A dependence.
We present azimuthal angular correlations between charged hadrons and energy deposited in calorim... more We present azimuthal angular correlations between charged hadrons and energy deposited in calorimeter towers in central d+Au and minimum bias p+p collisions at sqrt[s_{NN}]=200 GeV. The charged hadron is measured at midrapidity |η|<0.35, and the energy is measured at large rapidity (-3.7<η<-3.1, Au-going direction). An enhanced near-side angular correlation across…
The standard model (SM) of particle physics is spectacularly successful, yet the measured value o... more The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment (g − 2)µ deviates from SM calculations by 3.6σ. Several theoretical models attribute this to the existence of a "dark photon," an additional U(1) gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, U , in π 0 , η → γe + e − decays and obtained upper limits of O(2 × 10 −6) on U-γ mixing at 90% CL for the mass range 30 < mU < 90 MeV/c 2. Combined with other experimental limits, the remaining region in the U-γ mixing parameter space that can explain the (g − 2)µ deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of 29 < mU < 32 MeV/c 2 remaining.
Ion backflow in thick GEM-based detectors of single photons
Journal of Instrumentation, 2013
Photon detectors based on micropattern gas detectors represent a new generation of gaseous photon... more Photon detectors based on micropattern gas detectors represent a new generation of gaseous photon detectors. In the context of a project to upgrade the gas photon detectors of COMPASS RICH-1, we are performing an R&D programme aimed both to establish the principles and to develop the engineering aspects of photon detectors based on multi-layer arrangements of thick GEMs electron multipliers coupled to a CsI photoconverter. In this context, a reduced rate of the backflow of the positive ions generated in the multiplication process is required to overcome the critical issues related to the bombardment of the CsI photoconverter by ions. Our studies devoted to develop detector architectures able to provide reduced ion backflow rates are reported.
First measurement of the cross-section ratio Rdp(0) in charge-exchange (np) reactions on H2/D2 at... more First measurement of the cross-section ratio Rdp(0) in charge-exchange (np) reactions on H2/D2 at 0 o and Tn-1 GeV Dubna "Delta-Sigma experiment"
Measurement of direct photon v_2 in sqrt(s_NN)=200 GeV Au+Au collisions
arXiv: Nuclear Experiment, 2011
The second Fourier component v_2 of the azimuthal anisotropy with respect to the reaction plane h... more The second Fourier component v_2 of the azimuthal anisotropy with respect to the reaction plane has been measured for direct photons at midrapidity and transverse momentum (p_T) of 1.15 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 we find that for p_T > 4 GeV/c, the anisotropy for direct photons is consistent with zero and current uncertainties prevent a conclusive test of predicted small v_2 values from jet conversion and fragmentation photons. 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.
Citation Adare, A. et al. " Suppression of Back-to-Back Hadron Pairs at Forward Rapidity in ... more Citation Adare, A. et al. " Suppression of Back-to-Back Hadron Pairs at Forward Rapidity in d+Au Collisions at sqrt[s_{NN}]=200GeV. Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters.
Azimuthal angle (∆φ) correlations are presented for charged hadrons from dijets for 0.4 < pT < 10... more Azimuthal angle (∆φ) correlations are presented for charged hadrons from dijets for 0.4 < pT < 10 GeV/c in Au+Au collisions at √ sNN = 200 GeV. With increasing pT , the away-side distribution evolves from a broad to a concave shape, then to a convex shape. Comparisons to p + p data suggest that the away-side can be divided into a partially suppressed "head" region centered at ∆φ ∼ π, and an enhanced "shoulder" region centered at ∆φ ∼ π ± 1.1. The pT spectrum for the "head" region softens toward central collisions, consistent with the onset of jet quenching. The spectral slope for the "shoulder" region is independent of centrality and trigger pT , which offers constraints on energy transport mechanisms and suggests that the "shoulder" region contains the medium response to energetic jets.
Neutral pion transverse momentum (pT) spectra at midrapidity (|y| ≤ 0.35) were measured in Cu+Cu ... more Neutral pion transverse momentum (pT) spectra at midrapidity (|y| ≤ 0.35) were measured in Cu+Cu collisions at √ sNN = 22.4, 62.4, and 200 GeV. Relative to π 0 yields in p+p collisions scaled by the number of inelastic nucleon-nucleon collisions (N coll) the π 0 yields for pT > ∼ 2 GeV/c in central Cu+Cu collisions are suppressed at 62.4 and 200 GeV whereas an enhancement is observed at 22.4 GeV. A comparison with a jet quenching model suggests that final state parton energyloss dominates in central Cu+Cu collisions at 62.4 GeV and 200 GeV, while the enhancement at 22.4 GeV is consistent with nuclear modifications in the initial state alone.
Identified charged hadron production in p plus p collisions at root s = 200 and 62 . 4 GeV
Transverse momentum distributions and yields for pi(+/-), K-+/-, p, and (p) over bar in p + p col... more Transverse momentum distributions and yields for pi(+/-), K-+/-, p, and (p) over bar in p + p collisions at root s = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). These data provide important baseline spectra for comparisons with identified particle spectra in heavy ion collisions at RHIC. We present the inverse slope parameter T-inv, mean transverse momentum < p(T)>, and yield per unit rapidity dN/dy at each energy, and compare them to other measurements at different root s in p + p and p + (p) over bar collisions. We also present the scaling properties such as m(T) scaling and x(T) scaling on the p(T) spectra between different energies. To discuss the mechanism of the particle production in p + p collisions, the measured spectra are compared to next-toleading-order or next-to-leading-logarithmic perturbative quantum chromodynamics calculations. Disciplines Nuclear | Physics Comments This article is publis...
Measurement of the higher-order anisotropic flow coefficients for identified hadrons in Au plus Au collisions at root s ( NN ) = 200 GeV
Measurements of the anisotropic flow coefficients v(2){Psi(2)}, v(3){Psi(3)}, v(4){Psi(4)}, and v... more Measurements of the anisotropic flow coefficients v(2){Psi(2)}, v(3){Psi(3)}, v(4){Psi(4)}, and v(4){Psi(2)} for identified particles (pi(+/-), K-+/-, and p + (p) over bar) at midrapidity, obtained relative to the event planes Psi(m) at forward rapidities in Au + Au collisions at root s(NN) = 200 GeV, are presented as a function of collision centrality and particle transverse momenta p(T). The v(n) coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic n, a modified valence quark-number N-q scaling [plotting v(n){Psi(m)}/(N-q)(n/2) versus transverse kinetic energies (KET)/N-q] is observed to yield a single curve for all the measured particle species for a broad range of KET. A simultaneous blast-wave model fit to the observed v(n){Psi(m)}(p(T)) coefficients and published particle spectra identifies radial flow anisotropies rho(n){Psi(m)} and spatial eccentricities s(n){Psi(m)} at freeze-out. Thes...
Systematic study of charged-pion and kaon femtoscopy in Au plus Au collisions at root s ( NN ) = 200 GeV
We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at ro... more We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at root s(NN) = 200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthalangle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations. Disciplines Nuclear | Physics Comments This is an article from Physical Review C 92 (2015): 034914, doi:10.1103/PhysRevC.92.034914. Posted with permission. Authors Andrew Adare, Nicole Apadula, Sarah C. Campbell, John C. Hill, Nels J. Hotvedt, Todd Kempel, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Mila...
We report the measurement of the transverse momentum dependence of inclusive J/psi polarization i... more We report the measurement of the transverse momentum dependence of inclusive J/psi polarization in p + p collisions at root s = 200 GeV performed by the PHENIX Experiment at the Relativistic Heavy Ion Collider. The J/psi polarization is studied in the helicity, Gottfried-Jackson, and Collins-Soper frames for p(T) < 5 GeV/c and vertical bar y vertical bar < 0.35. The polarization in the helicity and Gottfried-Jackson frames is consistent with zero for all transverse momenta, with a slight (1.8 sigma) trend towards longitudinal polarization for transverse momenta above 2 GeV/c. No conclusion is allowed due to the limited acceptance in the Collins-Soper frame and the uncertainties of the current data. The results are compared to observations for other collision systems and center of mass energies and to different quarkonia production models. Disciplines Elementary Particles and Fields and String Theory | Physics Comments This article is published as Adare, A., S. Afanasiev, C. Ai...
Differential measurements of elliptic flow (v(2)) for Au+Au and Cu+Cu collisions at root s(NN)=20... more Differential measurements of elliptic flow (v(2)) for Au+Au and Cu+Cu collisions at root s(NN)=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v(2) with eccentricity, system size, and transverse kinetic energy (KET). For KET equivalent to m(T)-m up to similar to 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KET mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v(2) for both mesons and baryons over the full KET range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KET, rather than transverse momentum. Disciplines Elementary Particles and Fields and String Theory | Physics Comments This article is published as Adare, A., S. Afanasiev, C. Aidala, N. N. Ajitanand, Y. Akiba, H. Al-Bataineh, J. Alexander et al. "Scaling properties of azimuthal anisotropy in Au+ Au and Cu+ Cu collisions at s NN= 200 GeV." Phys...
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