Serguei Afanasiev

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (pT), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high pT. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.

The centrality dependence of transverse momentum distributions and yields for ± , K ± , p, and p ¯in Au + Au collisions at ͱ s NN = 200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider.We observe a clear particle mass dependence of the shapes of transverse momentum spectra in central collisions below ϳ2 GeV/ c in p T .Both mean transverse momenta and particle yields per participant pair increase from peripheral to midcentral and saturate at the most central collisions for all particle species.We also measure particle ratios of -/ + , K -/ K + , p ¯/ p, K / , p / , and p ¯/ as a function of p T and collision centrality.The ratios of equal mass particle yields are independent of p T and centrality within the experimental uncertainties.In central collisions at intermediate transverse momenta ϳ1.5-

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.

Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80, and 158 A GeV are presented. These are compared with data at lower and higher energies as well as with results from p+p interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with s1/4NN with a change of slope starting in the region 15–40 A GeV. The change from pion suppression with respect to p+p interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV. A nonmonotonic energy dependence of the ratio of K+ to π+ yields is observed, with a maximum close to 40A GeV and an indication of a nearly constant value at higher energies. The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.Received 6 May 2002DOI:https://doi.org/10.1103/PhysRevC.66.054902©2002 American Physical Society

The production of low mass e+e- pairs for m_{e+e-} < 300 MeV/c^2 and 1 < p_T <5 GeV/c is measured in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. Enhanced yield above hadronic sources is observed. Treating the excess as internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of direct photon yield over p+p is exponential in transverse momentum, with inverse slope T = 221 +/- 19 (stat) +/- 19 (syst) MeV. Hydrodynamical models with initial temperatures ranging from 300--600 MeV at times of ~ 0.6 - 0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at ~ 170 MeV.

Azimuthal angle (Δϕ) correlations are presented for a broad range of transverse momentum (0.4<pT<10 GeV/c) and centrality (0–92%) selections for charged hadrons from dijets in Au+Au collisions at √sNN=200 GeV. With increasing pT, the away-side Δϕ distribution evolves from a broad and relatively flat shape to a concave shape, then to a convex shape. Comparisons with p+p data suggest that the away-side distribution can be divided into a partially suppressed "head" region centered at Δϕ~π, and an enhanced "shoulder" region centered at Δϕ~π±1.1. The pT spectrum for the associated hadrons in the head region softens toward central collisions. The spectral slope for the shoulder region is independent of centrality and trigger pT. The properties of the near-side distributions are also modified relative to those in p+p collisions, reflected by the broadening of the jet shape in Δϕ and Δη, and an enhancement of the per-trigger yield. However, these modifications seem to be limited to pT≲4 GeV/c, above which both the hadron pair shape and per-trigger yield become similar to p+p collisions. These observations suggest that both the away- and near-side distributions contain a jet fragmentation component which dominates for pT≳5 GeV/c and a medium-induced component which is important for pT≲4 GeV/c. We also quantify the role of jets at intermediate and low pT through the yield of jet-induced pairs in comparison with binary scaled p+p pair yield. The yield of jet-induced pairs is suppressed at high pair proxy energy (sum of the pT magnitudes of the two hadrons) and is enhanced at low pair proxy energy. The former is consistent with jet quenching; the latter is consistent with the enhancement of soft hadron pairs due to transport of lost energy to lower pT.31 MoreReceived 30 January 2008DOI:https://doi.org/10.1103/PhysRevC.78.014901©2008 American Physical Society

Transverse momentum (p^e_T) spectra of electrons from semileptonic weak decays of heavy flavor mesons in the range of 0.3 < p^e_T < 9.0 GeV/c have been measured at mid-rapidity (|eta| < 0.35) by the PHENIX experiment at the Relativistic Heavy Ion Collider in p+p and Au+Au collisions at sqrt(s_NN)=200 GeV. The nuclear modification factor R_AA with respect to p+p collisions indicates substantial energy loss of heavy quarks in the produced medium. In addition, the azimuthal anisotropy parameter v_2 has been measured for 0.3 < p^e_T < 5.0 GeV/c in Au+Au collisions. Comparisons of R_AA and v_2 are made to various model calculations.

The PHENIX experiment has measured midrapidity ([FORMULA: SEE TEXT]) transverse momentum spectra ([FORMULA: SEE TEXT]) of electrons as a function of centrality in Au+Au collisions at [FORMULA: SEE TEXT]. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi0 and eta mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high pT is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.

Inclusive transverse momentum spectra of eta mesons have been measured within p(T) = 2-10 GeV/c at midrapidity by the PHENIX experiment in Au + Au collisions at square root S(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au + Au, d + Au, and p + p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi0. The ratio of eta to pi0 spectra at high p(T) amounts to 0.40 < R(eta/pi)0 < 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e+e- collisions.

J/psi production in p+p collisions at square root s=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over a rapidity range of -2.2<y<2.2 and a transverse momentum range of 0<pT<9 GeV/c. The size of the present data set allows a detailed measurement of both the pT and the rapidity distributions and is sufficient to constrain production models. The total cross section times the branching ratio is Bll sigma pp J/psi=178+/-3stat+/-53sys+/-18norm nb.

Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au Au collisions at s NN p 200 GeV.The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision.Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R out =R side is within 0.8-1.1 for 0:25 < hk T i < 1:2 GeV=c.The centrality dependence of all radii is well described by a linear scaling in N 1=3 part

The dependence of transverse momentum spectra of neutral pions and $\ensuremath{\eta}$ mesons with ${p}_{T}&lt;16\text{ }\text{ }\mathrm{GeV}/c$ and ${p}_{T}&lt;12\text{ }\text{ }\mathrm{GeV}/c$, respectively, on the centrality of the collision has been measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) in $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$. The measured yields are compared to those in $p+p$ collisions at the same $\sqrt{{s}_{NN}}$ scaled by the number of underlying nucleon-nucleon collisions in $d+\mathrm{Au}$. At all centralities, the yield ratios show no suppression, in contrast to the strong suppression seen for central $\mathrm{Au}+\mathrm{Au}$ collisions at RHIC. Only a weak ${p}_{T}$ and centrality dependence can be observed.

We present the first measurement of elliptic (v(2)) and triangular (v(3)) flow in high-multiplicity (3)He+Au collisions at √(s(NN))=200 GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in (3)He+Au and in p+p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the (3)He+Au system. The collective behavior is quantified in terms of elliptic v(2) and triangular v(3) anisotropy coefficients measured with respect to their corresponding event planes. The v(2) values are comparable to those previously measured in d+Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three (3)He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.

Cross sections for midrapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for transverse momenta of 3 < pT < 16 GeV/c. Next-to-leading order perturbative QCD (pQCD) describes the data well for pT >5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for pT >7 GeV/c.

The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au+Au collisions at √sNN=200 GeV down to pT=0.4 GeV/c. Photons are detected via photon conversions to e+e− pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low pT. We find an excess of direct photons above the Ncoll-scaled yield measured in p+p collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240MeV/c in the pT range 0.6–2.0 GeV/c. While the shape of the pT distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with Nαpart, where α=1.38±0.03(stat)±0.07(syst).3 MoreReceived 23 May 2014Revised 16 March 2015DOI:https://doi.org/10.1103/PhysRevC.91.064904©2015 American Physical Society

Yields and phase space distributions of φ-mesons emitted from p+p (minimum bias trigger), p+Pb (at various centralities) and central Pb+Pb collisions are reported (Ebeam=158AGeV). The decay φ→K+K− was used for identification. The φ/π ratio is found to increase by a factor of 3.0±0.7 from inelastic p+p to central Pb+Pb. Significant enhancement in this ratio is also observed in subclasses of p+p events (characterized by high charged-particle multiplicity) as well as in the forward hemisphere of central p+Pb collisions. In Pb+Pb no shift or significant broadening of the φ-peak is seen.

The PHENIX experiment has measured midrapidity transverse momentum spectra (0.4<p(T)<4.0 GeV/c) of single electrons as a function of centrality in Au+Au collisions at sqrt[s(NN)]=200 GeV. Contributions from photon conversions and Dalitz decays of light neutral mesons are measured by introducing a thin (1.7% X0) converter into the PHENIX acceptance and are statistically removed. The subtracted nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons containing heavy quarks, mainly charm at lower p(T). For all centralities, the charm production cross section is found to scale with the nuclear overlap function, T(AA). For minimum-bias collisions the charm cross section per binary collision is N(cc )/T(AA)=622+/-57(stat)+/-160(syst) microb.

Differential elliptic flow (v2) for ϕ mesons and (anti)deuterons (¯d)d is measured for Au+Au collisions at √sNN=200 GeV. The v2 for ϕ mesons follows the trend of lighter π± and K± mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v2 values for (¯d)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v2 per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.Received 14 March 2007DOI:https://doi.org/10.1103/PhysRevLett.99.052301©2007 American Physical Society

Yields for J/psi production in Cu+Cu collisions at sqrt s_NN=200 GeV have been measured over the rapidity range |y|<2.2 and compared with results in p+p and Au+Au collisions at the same energy. The Cu+Cu data offer greatly improved precision over existing Au+Au data for J/psi production in collisions with small to intermediate numbers of participants, in the range where the quark-gluon plasma transition threshold is predicted to lie. Cold nuclear matter estimates based on ad hoc fits to d+Au data describe the Cu+Cu data up to N_part approximately 50, corresponding to a Bjorken energy density of at least 1.5 GeV/fm(3).

We present the first measurement of photoproduction of J/psi and of two-photon production of high-mass e+e- pairs in electromagnetic (or ultra-peripheral) nucleus-nucleus interactions, using Au+Au data at sqrt(s_NN) = 200 GeV. The events are tagged with forward neutrons emitted following Coulomb excitation of one or both Au^{star} nuclei. The event sample consists of 28 events with m_{e+e-} > 2 GeV/c^2 with zero like-sign background. The measured cross sections at midrapidity of d\sigma / dy (J/psi + Xn, y=0) = 76 +/- 33 (stat) +/- 11 (syst) micro b and d^2\sigma/dm dy (e^+e^- + Xn, y=0) = 86 +/- 23 (stat) +/- 16 (syst) micro b/(GeV/c^2) for m_{e+e-} \in [2.0,2.8] GeV/c^2 are consistent with various theoretical predictions.

The PHENIX experiment has measured the suppression of semi-inclusive single high-transverse-momentum π0's in Au+Au collisions at √sNN=200 GeV. The present understanding of this suppression is in terms of energy loss of the parent (fragmenting) parton in a dense color-charge medium. We have performed a quantitative comparison between various parton energy-loss models and our experimental data. The statistical point-to-point uncorrelated as well as correlated systematic uncertainties are taken into account in the comparison. We detail this methodology and the resulting constraint on the model parameters, such as the initial color-charge density dNg/dy, the medium transport coefficient ⟨^q⟩, or the initial energy-loss parameter ε0. We find that high-transverse-momentum π0 suppression in Au+Au collisions has sufficient precision to constrain these model-dependent parameters at the ±20–25% (one standard deviation) level. These constraints include only the experimental uncertainties, and further studies are needed to compute the corresponding theoretical uncertainties.2 MoreReceived 10 January 2008DOI:https://doi.org/10.1103/PhysRevC.77.064907©2008 American Physical Society

We have measured the azimuthal anisotropy of π⁰ production for 1<p(T)<18 GeV/c for Au+Au collisions at sqrt((s)NN)=200 GeV. The observed anisotropy shows a gradual decrease for 3≲p(T)≲7-10 GeV/c, but remains positive beyond 10 GeV/c. The magnitude of this anisotropy is underpredicted, up to at least ∼10 GeV/c, by current perturbative QCD (PQCD) energy-loss model calculations. An estimate of the increase in anisotropy expected from initial-geometry modification due to gluon saturation effects and fluctuations is insufficient to account for this discrepancy. Calculations that implement a path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

We present measurements of $J/\ensuremath{\psi}$ yields in $d+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$ recorded by the PHENIX experiment and compare them with yields in $p+p$ collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in $J/\ensuremath{\psi}$ rapidity ($\ensuremath{-}2.2&lt;y&lt;2.4$) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

Measurements of neutral pion (π0) production at midrapidity in √sNN=200 GeV Au+Au collisions as a function of transverse momentum, pT, collision centrality, and angle with respect to reaction plane are presented. The data represent the final π0 results from the PHENIX experiment for the first RHIC Au+Au run at design center-of-mass energy. They include additional data obtained using the PHENIX Level-2 trigger with more than a factor of 3 increase in statistics over previously published results for pT>6 GeV/c. We evaluate the suppression in the yield of high-pT π0's relative to pointlike scaling expectations using the nuclear modification factor RAA. We present the pT dependence of RAA for nine bins in collision centrality. We separately integrate RAA over larger pT bins to show more precisely the centrality dependence of the high-pT suppression. We then evaluate the dependence of the high-pT suppression on the emission angle Δϕ of the pions with respect to event reaction plane for seven bins in collision centrality. We show that the yields of high-pT π0's vary strongly with Δϕ, consistent with prior measurements [1,2]. We show that this variation persists in the most peripheral bin accessible in this analysis. For the peripheral bins we observe no suppression for neutral pions produced aligned with the reaction plane, whereas the yield of π0's produced perpendicular to the reaction plane is suppressed by a factor of ~2. We analyze the combined centrality and Δϕ dependence of the π0 suppression in different pT bins using different possible descriptions of parton energy loss dependence on jet path-length averages to determine whether a single geometric picture can explain the observed suppression pattern.14 MoreReceived 7 November 2006DOI:https://doi.org/10.1103/PhysRevC.76.034904©2007 American Physical Society

The PHENIX experiment presents results from the RHIC 2006 run with polarized $p+p$ collisions at $\sqrt{s}=62.4\text{ }\text{ }\mathrm{GeV}$, for inclusive ${\ensuremath{\pi}}^{0}$ production at midrapidity. Unpolarized cross section results are measured for transverse momenta ${p}_{T}=0.5$ to $7\text{ }\text{ }\mathrm{GeV}/c$. Next-to-leading order perturbative quantum chromodynamics calculations are compared with the data, and while the calculations are consistent with the measurements, next-to-leading logarithmic corrections improve the agreement. Double helicity asymmetries ${A}_{LL}$ are presented for ${p}_{T}=1$ to $4\text{ }\text{ }\mathrm{GeV}/c$ and probe the higher range of Bjorken $x$ of the gluon (${x}_{g}$) with better statistical precision than our previous measurements at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$. These measurements are sensitive to the gluon polarization in the proton for $0.06&lt;{x}_{g}&lt;0.4$.

Differential measurements of the elliptic (v(2)) and hexadecapole (v(4)) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p(T)) and collision centrality or number of participant nucleons (N(part)) for Au+Au collisions at sq.rt(s(NN))=200 GeV. The v(2,4) measurements at pseudorapidity |η|≤0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0<|η|<3.9, show good agreement, indicating the absence of significant Δη-dependent nonflow correlations. Sizable values for v(4)(p(T)) are observed with a ratio v(4)(p(T),N(part))/v(2)(2)(p(T),N(part))≈0.8 for 50≲N(part)≲200, which is compatible with the combined effects of a finite viscosity and initial eccentricity fluctuations. For N(part)≳200 this ratio increases up to 1.7 in the most central collisions.

Inclusive transverse momentum spectra of \ensuremath{\eta} mesons in the range ${p}_{T}\ensuremath{\approx}2$--12 GeV/$c$ have been measured at midrapidity ($|\ensuremath{\eta}|&lt;0.35$) by the PHENIX experiment at RHIC in $p+p,d$+Au, and Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV. The \ensuremath{\eta} mesons are reconstructed through their $\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma} \ensuremath{\gamma}$ channel for the three colliding systems as well as through the $\ensuremath{\eta}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay mode in $p+p$ and $d$+Au collisions. The nuclear modification factor in $d$+Au collisions, ${R}_{d\mathrm{Au}}({p}_{T})\ensuremath{\approx}1.0$--1.1, suggests at most only modest ${p}_{T}$ broadening (``Cronin enhancement''). In central Au+Au reactions, the \ensuremath{\eta} yields are significantly suppressed, with ${R}_{\mathrm{AuAu}}({p}_{T})\ensuremath{\approx}0.2$. The ratio of \ensuremath{\eta} to ${\ensuremath{\pi}}^{0}$ yields is approximately constant as a function of ${p}_{T}$ for the three colliding systems in agreement with the high-${p}_{T}$ world average of ${R}_{\ensuremath{\eta}/{\ensuremath{\pi}}^{0}}\ensuremath{\approx}0.5$ in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies ($\sqrt{{s}_{\mathit{NN}}}\ensuremath{\approx}3$--1800 GeV) as well as, for high scaled momentum ${x}_{p}$, in ${e}^{+}{e}^{\ensuremath{-}}$ annihilations at $\sqrt{s}=91.2$ GeV. These results are consistent with a scenario where high-${p}_{T}$ \ensuremath{\eta} production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (${\ensuremath{\pi}}^{0},\ensuremath{\eta}$) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.

The MultiPurpose Detector (MPD) is designed to study heavy-ion collisions at the Nuclotron-based heavy Ion Collider fAcility (NICA) at JINR, Dubna. Its main components located inside a superconducting solenoid are a tracking system composed of a silicon microstrip vertex detector followed by a large volume time-projection chamber, a time-of-flight system for particle identification and a barrel electromagnetic calorimeter. A zero degree hadron calorimeter is designed specifically to measure the energy of spectators. In this paper, all parts of the apparatus are described and their tracking and particle identification (PID) parameters are discussed in some detail.

We present inclusive charged hadron elliptic flow v_2 measured over the pseudorapidity range |\eta| < 0.35 in Au+Au collisions at sqrt(s_NN) = 200 GeV. Results for v_2 are presented over a broad range of transverse momentum (p_T = 0.2-8.0 GeV/c) and centrality (0-60%). In order to study non-flow effects that are not correlated with the reaction plane, as well as the fluctuations of v_2, we compare two different analysis methods: (1) event plane method from two independent sub-detectors at forward (|\eta| = 3.1-3.9) and beam (|\eta| > 6.5) pseudorapidities and (2) two-particle cumulant method extracted using correlations between particles detected at midrapidity. The two event-plane results are consistent within systematic uncertainties over the measured p_T and in centrality 0-40%. There is at most 20% difference of the v_2 between the two event plane methods in peripheral (40-60%) collisions. The comparisons between the two-particle cumulant results and the standard event plane measurements are discussed.

PHENIX has measured the electron–positron pair mass spectrum from 0 to 8GeV/c2 in p+p collisions at s=200GeV. The contributions from light meson decays to e+e− pairs have been determined based on measurements of hadron production cross sections by PHENIX. Within the systematic uncertainty of ∼20% they account for all e+e− pairs in the mass region below ∼1GeV/c2. The e+e− pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544±39(stat)±142(syst)±200(model)μb, which is consistent with QCD calculations and measurements of single leptons by PHENIX.

Measurements of the anisotropy parameter ${v}_{2}$ of identified hadrons (pions, kaons, and protons) as a function of centrality, transverse momentum ${p}_{T}$, and transverse kinetic energy KE${}_{T}$ at midrapidity ($|\ensuremath{\eta}|&lt;0.35$) in Au + Au collisions at $\sqrt{{s}_{NN}}=200$ GeV are presented. Pions and protons are identified up to ${p}_{T}=$ 6 GeV$/c$, and kaons up to ${p}_{T}=$ 4 GeV$/c$, by combining information from time-of-flight and aerogel \ifmmode \check{C}\else \v{C}\fi{}erenkov detectors in the PHENIX Experiment. The scaling of ${v}_{2}$ with the number of valence quarks (${n}_{q}$) has been studied in different centrality bins as a function of transverse momentum and transverse kinetic energy. A deviation from previously observed quark-number scaling is observed at large values of KE${}_{T}/{n}_{q}$ in noncentral Au + Au collisions ($20--60%$), but this scaling remains valid in central collisions ($0--10%$).

Measurements of transverse-single-spin asymmetries (${A}_{N}$) in $p+p$ collisions at $\sqrt{s}=62.4$ and 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider are presented. At midrapidity, ${A}_{N}$ is measured for neutral pion and eta mesons reconstructed from diphoton decay, and, at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of ${A}_{N}$ at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in $\sqrt{s}$ and ${p}_{T}$, and it is found that the asymmetries depend only weakly on $\sqrt{s}$. The origin of the forward ${A}_{N}$ is presently not understood quantitatively. The extended reach to higher ${p}_{T}$ probes the transition between transverse momentum dependent effects at low ${p}_{T}$ and multiparton dynamics at high ${p}_{T}$.

We present measured J/psi production rates in d+Au collisions at sqrt(s_NN) = 200 GeV over a broad range of transverse momentum (p_T=0-14 GeV/c) and rapidity (-2.2<y<2.2). We construct the nuclear-modification factor R_dAu for these kinematics and as a function of collision centrality (related to impact parameter for the R_dAu collision). We find that the modification is largest for collisions with small impact parameters, and observe a suppression (R_dAu<1) for p_T<4 GeV/c at positive rapidities. At negative rapidity we observe a suppression for p_T<2 GeV/c then an enhancement (R_dAu>1) for p_T>2 GeV/c. The observed enhancement at negative rapidity has implications for the observed modification in heavy-ion collisions at high p_T.

Measurements of the midrapidity transverse energy distribution, $d\Et/d\eta$, are presented for $p$$+$$p$, $d$$+$Au, and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV and additionally for Au$+$Au collisions at $\sqrt{s_{_{NN}}}=62.4$ and 130 GeV. The $d\Et/d\eta$ distributions are first compared with the number of nucleon participants $N_{\rm part}$, number of binary collisions $N_{\rm coll}$, and number of constituent-quark participants $N_{qp}$ calculated from a Glauber model based on the nuclear geometry. For Au$+$Au, $\mean{d\Et/d\eta}/N_{\rm part}$ increases with $N_{\rm part}$, while $\mean{d\Et/d\eta}/N_{qp}$ is approximately constant for all three energies. This indicates that the two component ansatz, $dE_{T}/d\eta \propto (1-x) N_{\rm part}/2 + x N_{\rm coll}$, which has been used to represent $E_T$ distributions, is simply a proxy for $N_{qp}$, and that the $N_{\rm coll}$ term does not represent a hard-scattering component in $E_T$ distributions. The $dE_{T}/d\eta$ distributions of Au$+$Au and $d$$+$Au are then calculated from the measured $p$$+$$p$ $E_T$ distribution using two models that both reproduce the Au$+$Au data. However, while the number-of-constituent-quark-participant model agrees well with the $d$$+$Au data, the additive-quark model does not.

From superconductors to atomic nuclei, strongly-interacting many-body systems are ubiquitous in nature. Measuring the microscopic structure of such systems is a formidable challenge, often met by particle knockout scattering experiments. While such measurements are fundamental for mapping the structure of atomic nuclei, their interpretation is often challenged by quantum mechanical initial- and final-state interactions (ISI/FSI) of the incoming and scattered particles. Here we overcome this fundamental limitation by measuring the quasi-free scattering of 48 GeV/c 12C ions from hydrogen. The distribution of single protons is studied by detecting two protons at large angles in coincidence with an intact 11B nucleus. The 11B detection is shown to select the transparent part of the reaction and exclude the otherwise large ISI/FSI that would break the 11B apart. By further detecting residual 10B and 10Be nuclei, we also identified short-range correlated (SRC) nucleon-nucleon pairs, and provide direct experimental evidence for the separation of the pair wave-function from that of the residual many-body nuclear system. All measured reactions are well described by theoretical calculations that do not contain ISI/FSI distortions. Our results thus showcase a new ability to study the short-distance structure of short-lived radioactive atomic nuclei at the forthcoming FAIR and FRIB facilities. These studies will be pivotal for developing a ground-breaking microscopic understanding of the structure and properties of nuclei far from stability and the formation of visible matter in the universe.

PHENIX has measured the centrality dependence of midrapidity pion, kaon, and proton transverse momentum distributions in d + Au and p + p collisions at √ s NN = 200 GeV.The p + p data provide a reference for nuclear effects in d + Au and previously measured Au + Au collisions.Hadron production is enhanced in d + Au, relative to independent nucleon-nucleon scattering, as was observed in lower

We present the results of φ meson production in the K + K -decay channel from Au+Au collisions at √ s NN = 200 GeV as measured at midrapidity by the PHENIX detector at Brookhaven National Laboratory's Relativistic Heavy Ion Collider.Precision resonance centroid and width values are extracted as a function of collision centrality.No significant variation from the Particle Data Group accepted values is observed, contrary to some model predictions.The φ transverse mass spectra are fitted with a linear exponential function for which the derived inverse slope parameter is seen to be constant as a function of centrality.However, when these data are fitted by a hydrodynamic model the result is that the centrality-dependent freeze-out temperature and the expansion velocity values

width of the away-side peak is shown to be a convolution of j T with the fragmentation variable, z, and the partonic transverse momentum, k T .The hzi is determined through a combined analysis of the measured 0 inclusive and associated spectra using jet-fragmentation functions measured in e e ÿ collisions.The final extracted values of k T are then determined to also be independent of the trigger particle transverse momentum, over the

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity |y|<0.35 in p+p collisions at square root of s=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2<pT<7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D-->e(+/-)K(-/+)X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is sigma(bb)=3.2(-1.1)(+1.2)(stat)(-1.3)(+1.4)(syst)mub.

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).

Large parity-violating longitudinal single-spin asymmetries A(L)(e+) = -0.86(-0.14) (+0.30) and A(L)(e-) = 0.88(-0.71) (+0.12) are observed for inclusive high transverse momentum electrons and positrons in polarized p+p collisions at a center-of-mass energy of sqrt[s] = 500 GeV with the PHENIX detector at RHIC. These e± come mainly from the decay of W± and Z0 bosons, and their asymmetries directly demonstrate parity violation in the couplings of the W± to the light quarks. The observed electron and positron yields were used to estimate W± boson production cross sections for the e± channels of σ(pp → W+ X) × BR(W+ → e+ ν(e)) = 144.1 ± 21.2(stat)(-10.3) (+3.4) (syst) ± 21.6(norm) pb, and σ(pp → W- X) × BR(W- → e- ν[over ¯](e)) = 31.7 ± 12.1(stat)(-8.2) (+10.1) (syst) ± 4.8(norm) pb.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

The energy dependence of hadron production in central Pb+Pb collisions is presented and discussed. In particular, midrapidity $m_T$-spectra for $\pi^-$, $K^-$, $K^+$, $p$, $\bar{p}$, $d$, $\phi$, $\Lambda$ and $\bar{\Lambda}$ at 40, 80 and 158 $A$GeV are shown. In addition $\Xi$ and $\Omega$ spectra are available at 158 $A$GeV. The spectra allow to determine the thermal freeze-out temperature $T$ and the transverse flow velocity $\beta_T$ at the three energies. We do not observe a significant energy dependence of these parameters; furthermore there is no indication of early thermal freeze-out of $\Xi$ and $\Omega$ at 158 $A$GeV. Rapidity spectra for $\pi^-$, $K^-$, $K^+$ and $\phi$ at 40, 80 and 158 $A$GeV are shown, as well as first results on $\Omega$ rapidity distributions at 158 $A$GeV. The chemical freeze-out parameters $T$ and $\mu_B$ at the three energies are determined from the total yields. The parameters are close to the expected phase boundary in the SPS energy range and above. Using the total yields of kaons and lambdas, the energy dependence of the strangeness to pion ratio is discussed. A maximum in this ratio is found at 40 $A$GeV. This maximum could indicate the formation of deconfined matter at energies above 40 $A$GeV. A search for open charm in a large sample of 158 $A$GeV events is presented. No signal is observed. This result is compared to several model predictions.

We report on charged hadron production in deuteron-gold reactions at sqrt[s(NN)]=200 GeV. Our measurements in the deuteron direction cover 1.4<eta<2.2, referred to as forward rapidity, and in the gold direction -2.0<eta<-1.4, referred to as backward rapidity, and a transverse momentum range p(T)=0.5-4.0 GeV/c. We compare the relative yields for different deuteron-gold collision centrality classes. We observe a suppression relative to binary collision scaling at forward rapidity, sensitive to low momentum fraction (x) partons in the gold nucleus, and an enhancement at backward rapidity, sensitive to high momentum fraction partons in the gold nucleus.

Results of the production of Xi and Xi-bar hyperons in central Pb+Pb interactions at 158 GeV/c per nucleon are presented. This analysis utilises a global reconstruction procedure, which allows a measurement of 4pi integrated yields to be made for the first time. Inverse slope paramters, which are determined from an exponential fit to the transverse mass spectra, are shown. Central rapidity densities are found to be 1.49 +- 0.08 and 0.33 +- 0.04 per event per unit of rapidity for Xi and Xi-bar respectively. Yields integrated to full phase space are 4.12 +- 0.02 and 0.77 +- 0.04 for Xi and Xi-bar. The ratio of Xi-bar/Xi at mid-rapidity is 0.22 +- 0.03.

The production of deuterons and antideuterons in the transverse momentum range 1.1<p(T)<4.3 GeV/c at midrapidity in Au+Au collisions at square root of s(NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of p(T), which is consistent with an expanding collision zone. Comparing (anti)proton yields, p /p=0.73+/-0.01, with (anti)deuteron yields, d /d=0.47+/-0.03, we estimate that n /n=0.64+/-0.04. The nucleon phase space density is estimated from the coalescence measurement.

The differential cross section for the production of direct photons in p+p collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were measured in the transverse-momentum range from 5.5--25 GeV/c, extending the range beyond previous measurements. Event structure was studied with an isolation criterion. Next-to-leading-order perturbative-quantum-chromodynamics calculations give a good description of the spectrum. When the cross section is expressed versus x_T, the PHENIX data are seen to be in agreement with measurements from other experiments at different center-of-mass energies.

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, $\ensuremath{\Delta}g$. This study focuses on the extraction of the double-helicity asymmetry in $\ensuremath{\eta}$ production ($\stackrel{\ensuremath{\rightarrow}}{p}+\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\rightarrow}\ensuremath{\eta}+X$), the $\ensuremath{\eta}$ cross section, and the $\ensuremath{\eta}/{\ensuremath{\pi}}^{0}$ cross section ratio. The cross section and ratio measurements provide essential input for the extraction of fragmentation functions that are needed to access the helicity-dependent parton distribution functions.

Direct photons have been measured in $\sqrt{{s}_{{}_{NN}}}=200$ GeV $d+\text{Au}$ collisions at midrapidity. A wide ${p}_{T}$ range is covered by measurements of nearly real virtual photons ($1&lt;{p}_{T}&lt;6$ GeV/$c$) and real photons ($5&lt;{p}_{T}&lt;16$ GeV/$c$). The invariant yield of the direct photons in $d+\text{Au}$ collisions over the scaled $p+p$ cross section is consistent with unity. Theoretical calculations assuming standard cold-nuclear-matter effects describe the data well for the entire ${p}_{T}$ range. This indicates that the large enhancement of direct photons observed in $\mathrm{Au}+\mathrm{Au}$ collisions for $1.0&lt;{p}_{T}&lt;2.5$ GeV/$c$ is attributable to a source other than the initial-state nuclear effects.

Measurements of bottomonium production in heavy-ion and p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three Υ states, Υ(1S+2S+3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au+Au and p+p collisions at √sNN=200 GeV. The Υ(1S+2S+3S)→e+e− differential cross section at midrapidity was found to be Beedσ/dy=108±38(stat)±15(syst)±11(luminosity) pb in p+p collisions. The nuclear modification factor in the 30% most central Au+Au collisions indicates a suppression of the total Υ state yield relative to the extrapolation from p+p collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.10 MoreReceived 17 May 2014DOI:https://doi.org/10.1103/PhysRevC.91.024913©2015 American Physical Society

New PHENIX 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 ($\pi^{\pm}$, $K^{\pm}$, and $p+\bar{p}$) obtained relative to the event planes $\Psi_n$ in Au$+$Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV are presented as functions 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 $v_n/(n_q)^{n/2}$ versus ${\rm KE}_T/n_q$ is observed to yield a single curve for all the measured particle species for a broad range of transverse kinetic energies ${\rm KE}_T$. A simultaneous blast wave model fit to the observed particle spectra and $v_n(p_T)$ coefficients identifies spatial eccentricities $s_n$ at freeze-out, which are much smaller than the initial-state geometric values.

First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented.The yield of J/'s measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at ͱ s NN = 200 GeV is analyzed as a function of collision centrality.For this analysis we have studied 49.3ϫ 10 6 minimum bias Au-Au reactions.We present the J/ invariant yield dN/dy for peripheral and midcentral reactions.For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits.We compare these results with our J/ measurement from proton-proton reactions at the same energy.We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.

The azimuthal distribution of identified pi0 and inclusive photons has been measured in [FORMULA: SEE TEXT] Au+Au collisions with the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The second-harmonic parameter (nu2) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured pT range 1-6 GeV/c. An attempt is made to extract nu2 of direct photons.

New measurements by the PHENIX experiment at RHIC for eta production at midrapidity as a function of transverse momentum (p_T) and collision centrality in sqrt(s_NN) = 200 GeV Au+Au and p+p collisions are presented. They indicate nuclear modification factors (R_AA) that are similar both in magnitude and trend to those found in earlier pi^0 measurements. Linear fits to R_AA in the 5--20 GeV/c p_T region show that the slope is consistent with zero within two standard deviations at all centralities although a slow rise cannot be excluded. Having different statistical and systematic uncertainties the pi^0 and eta measurements are complementary at high p_T; thus, along with the extended p_T range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.

Background: Heavy-flavor production in p+p collisions tests perturbative-quantum-chromodynamics (pQCD) calculations. Modification of heavy-flavor production in heavy-ion collisions relative to binary-collision scaling from p+p results, quantified with the nuclear-modification factor (R_AA), provides information on both cold- and hot-nuclear-matter effects. Purpose: Determine transverse-momentum, pt, spectra and the corresponding R_AA for muons from heavy-flavor mesons decay in p+p and Cu+Cu collisions at sqrt(s_NN)=200 GeV and y=1.65. Method: Results are obtained using the semi-leptonic decay of heavy-flavor mesons into negative muons. The PHENIX muon-arm spectrometers measure the p_T spectra of inclusive muon candidates. Backgrounds, primarily due to light hadrons, are determined with a Monte-Carlo calculation using a set of input hadron distributions tuned to match measured-hadron distributions in the same detector and statistically subtracted. Results: The charm-production cross section in p+p collisions at sqrt{s}=200 GeV, integrated over pt and in the rapidity range 1.4<y<1.9 is found to be dsigma_ccbar/dy = 0.139 +/- 0.029 (stat) ^{+0.051}_{-0.058} (syst) mb. This result is consistent with calculations and with expectations based on the corresponding midrapidity charm-production cross section measured earlier by PHENIX. The R_AA for heavy-flavor muons in Cu+Cu collisions is measured in three centrality intervals for 1<pt<4 GeV/c. Suppression relative to binary-collision scaling (R_AA<1) increases with centrality. Conclusions: Within experimental and theoretical uncertainties, the measured heavy-flavor yield in p+p collisions is consistent with state-of-the-art pQCD calculations. Suppression in central Cu+Cu collisions suggests the presence of significant cold-nuclear-matter effects and final-state energy loss.

The PHENIX experiment at the Relativistic Heavy Ion Collider has performed a systematic study of $K_S^0$ and $K^{*0}$ meson production at midrapidity in $p$$+$$p$, $d$$+$Au, and Cu$+$Cu collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The $K_S^0$ and $K^{*0}$ mesons are reconstructed via their $K_S^0 \rightarrow \pi^0(\rightarrow \gamma\gamma)\pi^0(\rightarrow\gamma\gamma)$ and $K^{*0} \rightarrow K^{\pm}\pi^{\mp}$ decay modes, respectively. The measured transverse-momentum spectra are used to determine the nuclear modification factor of $K_S^0$ and $K^{*0}$ mesons in $d$$+$Au and Cu$+$Cu collisions at different centralities. In the $d$$+$Au collisions, the nuclear modification factor of $K_S^0$ and $K^{*0}$ mesons is almost constant as a function of transverse momentum and is consistent with unity showing that cold-nuclear-matter effects do not play a significant role in the measured kinematic range. In Cu$+$Cu collisions, within the uncertainties no nuclear modification is registered in peripheral collisions. In central collisions, both mesons show suppression relative to the expectations from the $p$$+$$p$ yield scaled by the number of binary nucleon-nucleon collisions in the Cu$+$Cu system. In the $p_T$ range 2--5 GeV/$c$, the strange mesons ($K_S^0$, $K^{*0}$) similarly to the $\phi$ meson with hidden strangeness, show an intermediate suppression between the more suppressed light quark mesons ($\pi^0$) and the nonsuppressed baryons ($p$, $\bar{p}$). At higher transverse momentum, $p_T>5$ GeV/$c$, production of all particles is similarly suppressed by a factor of $\approx$ 2.

Abstract As part of its HL-LHC upgrade program, the CMS collaboration is developing a High Granularity Calorimeter (CE) to replace the existing endcap calorimeters. The CE is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The calorimeter will be built with ∼30,000 hexagonal silicon modules. Prototype modules have been constructed with 6-inch hexagonal silicon sensors with cell areas of 1.1 cm 2 , and the SKIROC2-CMS readout ASIC. Beam tests of different sampling configurations were conducted with the prototype modules at DESY and CERN in 2017 and 2018. This paper describes the construction and commissioning of the CE calorimeter prototype, the silicon modules used in the construction, their basic performance, and the methods used for their calibration.

Abstract The upgrade of the CMS experiment for the high luminosity operation of the LHC comprises the replacement of the current endcap calorimeter by a high granularity sampling calorimeter (HGCAL). The electromagnetic section of the HGCAL is based on silicon sensors interspersed between lead and copper (or copper tungsten) absorbers. The hadronic section uses layers of stainless steel as an absorbing medium and silicon sensors as an active medium in the regions of high radiation exposure, and scintillator tiles directly read out by silicon photomultipliers in the remaining regions. As part of the development of the detector and its readout electronic components, a section of a silicon-based HGCAL prototype detector along with a section of the CALICE AHCAL prototype was exposed to muons, electrons and charged pions in beam test experiments at the H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology as foreseen for the HGCAL but with much finer longitudinal segmentation. The performance of the calorimeters in terms of energy response and resolution, longitudinal and transverse shower profiles is studied using negatively charged pions, and is compared to GEANT4 predictions. This is the first report summarizing results of hadronic showers measured by the HGCAL prototype using beam test data.

A measurement of direct photons in $p+p$ collisions at $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ is presented. A photon excess above background from ${\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\gamma}$, $\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma}+\ensuremath{\gamma}$ and other decays is observed in the transverse momentum range $5.5&lt;{p}_{\mathrm{T}}&lt;7\text{ }\text{ }\mathrm{GeV}/c$. The result is compared to a next-to-leading-order perturbative QCD calculation. Within errors, good agreement is found between the QCD calculation and the measured result.

Muon production at forward rapidity (1.5≤|η|≤1.8) has been measured by the PHENIX experiment over the transverse momentum range 1≤pT≤3 GeV/c in √s=200 GeV p+p collisions at the Relativistic Heavy Ion Collider. After statistically subtracting contributions from light hadron decays an excess remains which is attributed to the semileptonic decays of hadrons carrying heavy flavor, i.e. charm quarks or, at high pT, bottom quarks. The resulting muon spectrum from heavy flavor decays is compared to PYTHIA and a next-to-leading-order perturbative QCD calculation. PYTHIA is used to determine the charm quark spectrum that would produce the observed muon excess. The corresponding differential cross section for charm quark production at forward rapidity is determined to be dσc¯c/dy|y=1.6=0.243±0.013(stat.)±0.105(data syst.)+0.049−0.087(PYTHIA syst.) mb.11 MoreReceived 18 September 2006DOI:https://doi.org/10.1103/PhysRevD.76.092002©2007 American Physical Society

Correlations of charged hadrons of $1&lt;{p}_{T}&lt;10\text{ }\text{ }\mathrm{Gev}/c$ with high ${p}_{T}$ direct photons and ${\ensuremath{\pi}}^{0}$ mesons in the range $5&lt;{p}_{T}&lt;15\text{ }\text{ }\mathrm{Gev}/c$ are used to study jet fragmentation in the $\ensuremath{\gamma}+\mathrm{\text{jet}}$ and dijet channels, respectively. The magnitude of the partonic transverse momentum, ${k}_{T}$, is obtained by comparing to a model incorporating a Gaussian ${k}_{T}$ smearing. The sensitivity of the associated charged hadron spectra to the underlying fragmentation function is tested and the data are compared to calculations using recent global fit results. The shape of the direct photon-associated hadron spectrum as well as its charge asymmetry are found to be consistent with a sample dominated by quark-gluon Compton scattering. No significant evidence of fragmentation photon correlated production is observed within experimental uncertainties.

The three $\ensuremath{\Upsilon}$ states, $\ensuremath{\Upsilon}(1S+2S+3S)$, are measured in $d+\text{Au}$ and $p+p$ collisions at $\sqrt{{s}_{{}_{NN}}}=200$ GeV and rapidities $1.2&lt;|y|&lt;2.2$ by the PHENIX experiment at the Relativistic Heavy Ion Collider. Cross sections for the inclusive $\ensuremath{\Upsilon}(1S+2S+3S)$ production are obtained. The inclusive yields per binary collision for $d+\text{Au}$ collisions relative to those in $p+p$ collisions (${R}_{d\mathrm{Au}}$) are found to be $0.62\ifmmode\pm\else\textpm\fi{}0.26\phantom{\rule{0.28em}{0ex}}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.13\phantom{\rule{0.28em}{0ex}}(\mathrm{syst})$ in the gold-going direction and $0.91\ifmmode\pm\else\textpm\fi{}0.33\phantom{\rule{0.28em}{0ex}}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.16\phantom{\rule{0.28em}{0ex}}(\mathrm{syst})$ in the deuteron-going direction. The measured results are compared to a nuclear-shadowing model, EPS09 [Eskola et al., J. High Energy Phys. 04 (2009) 065], combined with a final-state breakup cross section, ${\ensuremath{\sigma}}_{\mathrm{br}}$, and compared to lower energy $p+A$ results. We also compare the results to the PHENIX $J/\ensuremath{\psi}$ results [Adare et al., Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity dependence of the observed $\ensuremath{\Upsilon}$ suppression is consistent with lower energy $p+A$ measurements.

In this review we first outline the basics of transport theory and its recent generalization to off-shell transport. We then present in some detail the main ingredients of any transport method using in particular the Giessen Boltzmann–Uehling–Uhlenbeck (GiBUU) implementation of this theory as an example. We discuss the potentials used, the ground state initialization and the collision term, including the in-medium modifications of the latter. The central part of this review covers applications of GiBUU to a wide class of reactions, starting from pion-induced reactions over proton and antiproton reactions on nuclei to heavy-ion collisions (up to about 30AGeV). A major part concerns also the description of photon-, electron- and neutrino-induced reactions (in the energy range from a few 100MeV to a few 100GeV). For this wide class of reactions GiBUU gives an excellent description with the same physics input and the same code being used. We argue that GiBUU is an indispensable tool for any investigation of nuclear reactions in which final-state interactions play a role. Studies of pion–nucleus interactions, nuclear fragmentation, heavy-ion reactions, hypernucleus formation, hadronization, color transparency, electron–nucleus collisions and neutrino–nucleus interactions are all possible applications of GiBUU and are discussed in this article.

Longitudinal density correlations of produced matter in Au+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV have been measured from the inclusive charged particle distributions as a function of pseudorapidity window sizes. The extracted $\ensuremath{\alpha}\ensuremath{\xi}$ parameter, related to the susceptibility of the density fluctuations in the long-wavelength limit, exhibits a nonmonotonic behavior as a function of the number of participant nucleons, ${N}_{\mathrm{part}}$. A local maximum is seen at ${N}_{\mathrm{part}}~90$, with corresponding energy density based on the Bjorken picture of ${\ensuremath{\epsilon}}_{\mathrm{Bj}}\ensuremath{\tau}~2.4$ GeV/(fm${}^{2}c)$ with a transverse area size of 60 fm${}^{2}$. This behavior may suggest a critical phase boundary based on the Ginzburg-Landau framework.

The PHENIX experiment at RHIC has measured the invariant cross section for \ensuremath{\omega}-meson production at midrapidity in the transverse momentum range $2.5&lt;{p}_{T}&lt;9.25$ GeV/$c$ in $p+p$ and $d$+Au collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV. Measurements in two decay channels ($\ensuremath{\omega}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and $\ensuremath{\omega}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$) yield consistent results, and the reconstructed \ensuremath{\omega} mass agrees with the accepted value within the ${p}_{T}$ range of the measurements. The $\ensuremath{\omega}/{\ensuremath{\pi}}^{0}$ ratio is found to be $0.85\ifmmode\pm\else\textpm\fi{}0.{05}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{09}^{\mathrm{sys}}$ in $p+p$ and $0.94\ifmmode\pm\else\textpm\fi{}0.{08}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{12}^{\mathrm{sys}}$ in $d$+Au collisions, independent of ${p}_{T}$. The nuclear modification factor ${R}_{d\mathrm{A}}^{\ensuremath{\omega}}$ is $1.03\ifmmode\pm\else\textpm\fi{}0.{12}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{21}^{\mathrm{sys}}$ and $0.83\ifmmode\pm\else\textpm\fi{}0.{21}^{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.{17}^{\mathrm{sys}}$ in minimum bias and central (0--20%) $d$+Au collisions, respectively.

We present measurements of the reduction of light output by plastic scintillators irradiated in the CMS detector during the 8 TeV run of the Large Hadron Collider and show that they indicate a strong dose rate effect. The damage for a given dose is larger for lower dose rate exposures. The results agree with previous measurements of dose rate effects, but are stronger due to the very low dose rates probed. We show that the scaling with dose rate is consistent with that expected from diffusion effects.

We present a systematic study of charged-pion and kaon interferometry in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{\mathit{NN}}}}=200$ 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 azimuthal-angle 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.

The dependence of the K+ and K− production on the number of nucleons involved in the annihilation process is investigated experimentally in the p¯ annihilation at rest on hydrogen, deuterium, 3He and 4He gas targets. Annihilations with any number of prongs (charged pions and kaons, protons and deuterons) are analyzed. Events with and without production of neutral mesons and with and without emission of fast neutrons (that is neutrons involved in the annihilation process) are recognized. The results are consistent with our previous ones on a more restricted sample of annihilation reactions and put in evidence that the strangeness production is lower or higher depending on the reaction channel. As a general trend, the strangeness production is higher in events without neutral mesons and still higher in events with the involvement of a higher number of nucleons. Both K+ and K− productions increase with the number of involved nucleons, but K+ much more. The maximum K+ production is observed in the reaction K+2π+2π−3n on 4He (with the involvement of 3–4 nucleons); compared with the production on hydrogen in the reaction K+π+2π−, the production on 4He is higher by a factor of 31.7±5.5. In the light of some theoretical speculations, this enhancement factor is too high to be explainable in terms of hadronic interactions and could be interpreted as a signature of quark deconfinement and of formation of a quark–gluon plasma.

In this paper we present recent results from the NA49 experiment for Λ and hyperons produced in central Pb + Pb collisions at 40, 80 and 158 A GeV. Transverse mass spectra and rapidity distributions for Λ are shown for all three energies. The shape of the rapidity distribution becomes flatter with increasing beam energy. The multiplicities at mid-rapidity as well as the total yields are studied as a function of collision energy including AGS measurements. The ratio Λ/π at mid-rapidity and in 4π has a maximum around 40 A GeV. In addition, rapidity distributions have been measured at 40 and 80 A GeV, which allows us to study the /Λ ratio.

The large acceptance and high momentum resolution as well as the significant particle identification capabilities of the NA49 experiment at the CERN SPS allow for a broad study of fluctuations and correlations in hadronic interactions. In the first part recent results on event-by-event charge and p_t fluctuations are presented. Charge fluctuations in central Pb+Pb reactions are investigated at three different beam energies (40, 80, and 158 AGeV), while for the p_t fluctuations the focus is put on the system size dependence at 158 AGeV. In the second part recent results on Bose Einstein correlations of h-h- pairs in minimum bias Pb+Pb reactions at 40 and 158 AGeV, as well as of K+K+ and K-K- pairs in central Pb+Pb collisions at 158 AGeV are shown. Additionally, other types of two particle correlations, namely pi p, Lambda p, and Lambda Lambda correlations, have been measured by the NA49 experiment. Finally, results on the energy and system size dependence of deuteron coalescence are discussed.

The azimuthal anisotropy coefficients ${v}_{2}$ and ${v}_{4}$ of ${\ensuremath{\pi}}^{0}$ and $\ensuremath{\eta}$ mesons are measured in Au + Au collisions at $\sqrt{{s}_{\mathit{\text{NN}}}}=200$ GeV as a function of transverse momentum ${p}_{T}$ (1--14 GeV/$c$) and centrality. The extracted ${v}_{2}$ coefficients are found to be consistent between the two meson species over the measured ${p}_{T}$ range. The ratio of ${v}_{4}/{v}_{2}^{2}$ for ${\ensuremath{\pi}}^{0}$ mesons is found to be independent of ${p}_{T}$ for 1--9 GeV/$c$, implying a lack of sensitivity of the ratio to the change of underlying physics with ${p}_{T}$. Furthermore, the ratio of ${v}_{4}/{v}_{2}^{2}$ is systematically larger in central collisions, which may reflect the combined effects of fluctuations in the initial collision geometry and finite viscosity in the evolving medium.

This work measures azimuthal correlations of electron-muon pairs, which are sensitive to the presence of heavy-quark hadron pairs, primarily cc\ifmmode\bar\else\textasciimacron\fi{}, that are produced in ultrarelativistic heavy-ion collisions. The results indicate that open-charm production is suppressed in deuteron on Au collisions compared to proton-proton collisions. This suggests that the cold nucleus is modifying the transport of heavy quarks or gluons in the nucleus.

We have measured direct photons for $p_T<5~$GeV/$c$ in minimum bias and 0\%--40\% most central events at midrapidity for Cu$+$Cu collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The $e^{+}e^{-}$ contribution from quasi-real direct virtual photons has been determined as an excess over the known hadronic contributions in the $e^{+}e^{-}$ mass distribution. A clear enhancement of photons over the binary scaled $p$$+$$p$ fit is observed for $p_T<4$ GeV/$c$ in Cu$+$Cu data. The $p_T$ spectra are consistent with the Au$+$Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the $p$$+$$p$ baseline are 285$\pm$53(stat)$\pm$57(syst)~MeV/$c$ and 333$\pm$72(stat)$\pm$45(syst)~MeV/$c$ for minimum bias and 0\%--40\% most central events, respectively. The rapidity density, $dN/dy$, of photons demonstrates the same power law as a function of $dN_{\rm ch}/d\eta$ observed in Au$+$Au at the same collision energy.

The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured open-heavy-flavor production in $\mathrm{Cu}+\mathrm{Cu}$ collisions at $\sqrt{{s}_{NN}}=200$ GeV through the measurement of electrons at midrapidity that originate from semileptonic decays of charm and bottom hadrons. In peripheral $\mathrm{Cu}+\mathrm{Cu}$ collisions an enhanced production of electrons is observed relative to $p+p$ collisions scaled by the number of binary collisions. In the transverse momentum range from 1 to 5 GeV/$c$ the nuclear modification factor is ${R}_{AA}\ensuremath{\sim}1.4$. As the system size increases to more central $\mathrm{Cu}+\mathrm{Cu}$ collisions, the enhancement gradually disappears and turns into a suppression. For ${p}_{T}&gt;3$ GeV/$c$, the suppression reaches ${R}_{AA}\ensuremath{\sim}0.8$ in the most central collisions. The ${p}_{T}$ and centrality dependence of ${R}_{AA}$ in $\mathrm{Cu}+\mathrm{Cu}$ collisions agree quantitatively with ${R}_{AA}$ in $d+\text{Au}$ and $\mathrm{Au}+\mathrm{Au}$ collisions, if compared at a similar number of participating nucleons $\ensuremath{\langle}{N}_{\mathrm{part}}\ensuremath{\rangle}$.

Experimental results on deuteron emission from central Pb+Pb collisions (Ebeam=158A GeV, fixed target), obtained by NA49 at the CERN SPS accelerator, are presented. The transverse mass mt distribution was measured near mid-rapidity (2.0<y<2.5) in the range of 0<mt−m0<0.9 GeV/c2 (0<pt<2.0 GeV/c) for the 4% most central collisions. An exponential fit gives an inverse slope Td=(450±30) MeV and a yield dNd/dy=0.34±0.03. The coalescence factor B2(mt=m0)=(3.5±1.0)·10−4 GeV2 and its mt-dependence are determined and discussed in terms of a model that includes the collective expansion of the source created in a collision. The derived Gaussian size parameter RG of the emission volume is consistent with earlier HBT results on the source of pion emission.

Bose-Einstein correlations of charged kaons were measured near mid-rapidity in central Pb+Pb collisions at 158 A$\cdot$GeV by the NA49 experiment at the CERN SPS. Source radii were extracted using the Yano-Koonin-Podgoretsky and Bertsch-Pratt parameterizations. The results are compared to published pion data. The measured $m_\perp$ dependence for kaons and pions is consistent with collective transverse expansion of the source and a freeze-out time of about 9.5 $fm$.

We report a measurement of $e^+e^-$ pairs from semileptonic heavy-flavor decays in $p$+$p$ collisions at $\sqrt{s_{NN}}=200$~GeV. The $e^+e^-$ pair yield from $b\bar{b}$ and $c\bar{c}$ is separated by exploiting a double differential fit done simultaneously in dielectron invariant mass and $p_T$. We used three different event generators, {\sc pythia}, {\sc mc@nlo}, and {\sc powheg}, to simulate the $e^+e^-$ spectra from $c\bar{c}$ and $b\bar{b}$ production. The data can be well described by all three generators within the detector acceptance. However, when using the generators to extrapolate to $4π$, significant differences are observed for the total cross section. These difference are less pronounced for $b\bar{b}$ than for $c\bar{c}$. The same model dependence was observed in already published $d$+$A$ data. The $p$+$p$ data are also directly compared with $d$+$A$ data in mass and $p_T$, and within the statistical accuracy no nuclear modification is seen.

The tensor analyzing power Ayy in inclusive breakup of 9 GeV/c deuterons on carbon has been measured at the detected proton angle of 85 mr. The analyzing power remains positive at the highest measured momentum of the proton in definite contradiction with the predictions of the existing models. The vector analyzing power Ay has been obtained simultaneously with Ayy.

Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot-dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whether the modification of the away-side-jet shape seen in hadron-hadron correlations is present when the trigger particle is from heavy-meson decay and whether the overall level of away-side jet suppression is consistent. We statistically subtract correlations of electrons arising from background sources from the inclusive electron-hadron correlations and obtain two-particle azimuthal correlations at sqrt(s_NN)=$200 GeV between electrons from heavy-flavor decay with charged hadrons in p+p and also first results in Au+Au collisions. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to p+p collisions.

Unpolarized cross sections and double-helicity asymmetries of single-inclusive positive and negative charged hadrons at midrapidity from p+p collisions at sqrt(s)=62.4 GeV are presented. The PHENIX measurements 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 ~< x_gluon ~< 0.2, is consistent with recent global parameterizations disfavoring large gluon polarization.

The angular dependence of the tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with a momentum of 9.0 GeV/c on hydrogen and carbon have been measured. The range of measurements corresponds to the baryonic resonance excitation with masses 2.2--2.6 GeV/c^2. The Ayy data being in good agreement with the previous results demonstrate an approximate $t$ scaling up to -1.5 (GeV/c)^2. The large values of A_y show a significant role of the spin-dependent part of the elementary amplitude of the NN->NN* reaction. The results of the experiment are compared with model predictions of the plane-wave impulse approximation.

The tensor analyzing power Ayy in inclusive breakup of 9.0 GeV/c deuterons on hydrogen and carbon has been measured at different emission angles of protons. The data are compared to calculations within the framework of light-front dynamics by using different deuteron wave functions. The results suggest that the relativistic deuteron structure may depend on more than one independent variable.

Measurements of transverse-single-spin asymmetries ($A_{N}$) in $p$$+$$p$ collisions at $\sqrt{s}=$62.4 and 200 GeV with the PHENIX detector at RHIC are presented. At midrapidity, $A_{N}$ is measured for neutral pion and eta mesons reconstructed from diphoton decay, and at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of $A_{N}$ at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in $\sqrt{s}$ and $p_T$, and it is found that the asymmetries depend only weakly on $\sqrt{s}$. The origin of the forward $A_{N}$ is presently not understood quantitatively. The extended reach to higher $p_T$ probes the transition between transverse momentum dependent effects at low $p_T$ and multi-parton dynamics at high $p_T$.

Abstract Relative permeabilities are very important for reservoir engineering, because these parameters highly influence waterflooding efficiency, oil/liquid production forecast and therefore economics of an asset. Evaluation of multiphase flow parameters from core data suffers from small REV and pointwise level of averaging. It distorts the actual flow conditions at the reservoir level, and their history matching from production data requires long history of waterflooding. The technological complexity of new oil reservoirs development rises the problem of determining the displacement effeciency (Edisp) and relative permeability functions (RP) in the downhole conditions for reliable evaluation of investment attractiveness of the asset and creating sound development of the project. This paper summarizes the experience and interpretation of two-phase well testing using OGRI RAS technology. Integrated well testing to determine Edisp and RP (for oil-water system) is based on the creation of two-phase (oil and water) multidirectional flows and repeatable recordings of pulsed neutron logging (PNL) to monitor changes in water saturation near wellbore. For reliable geophysical interpretation it is necessary to monitor changes in the water phase salinity in contact with formation water, injectied water and technological solutions. Integrated interpretation of such testing procedure is based on the numerical solution of direct and inverse problems in the two-dimensional, two-phase (oil-water), two (oil + water) or three (oil + water + salt) component statement. The experience of conducting and interpreting such tests for oil fields at the exploration stage and pilot projects in conditions of autonomy and arctic climate is delivered in the paper. Accumulated experience allowed us to justify the optimal design of the testing process, well preparation and the well testing procedure itself. Special schemes of downhole and wellhead equipment setup are devised for solving all the research problems without lifting operations. Original technical solutions for well completion and continuous pumping of water-based agent in arctic climate, with large permafrost interval and very low formation injectivity were also developed. Complex technique of joint geophysical and flow measurements interpretation in the course of well testing is substantiated. The effective numerical algorithms and software for solving inverse problems to identify oil and water RP at reservoir conditions in two-dimensional, two-phase (oil-water), two (oil + water) or three (oil + water + salt) component model were also proposed and validated. Significant effect of technological fluids penetration into the formation during well completion and tripping on reservoir water salinity in the near wellbore area is revealed, Simplified method of accounting for and controlling salinity changes during interaction between reservoir, injected and residual technological water phases is proposed. For the object tested, effective estimates of displacement efficiency and RP curves are obtained. These parameters substantially correct core data and provide more reliable prediction of water flooding system efficiency and assessment of the investment attractiveness of the asset.

Tensor Ayy and vector Ay analyzing powers in the inelastic scattering of deuterons with the momentum of 5.0 GeV/c on beryllium at an angle of 178 mr in the vicinity of the excitation of baryonic resonances with masses up to 1.8 GeV/c^2 have been measured. The Ayy data are in a good agreement with the previous data obtained at 4.5 and 5.5 GeV/c. The results of the experiment are compared with the predictions of the plane wave impulse approximation and \omega-meson exchange models.

New data on the tensor analyzing power Ayy of the 9Be(d,p)X reaction at an initial deuteron momentum of 5 GeV/c and a proton detection angle of 178 mr have been obtained at the JINR Synchrophasotron. The data obtained are compared with the relativistic calculations of the deuteron breakup process made in the framework of the light-front dynamics. We have managed to explain the new data with Karmanov's relativistic deuteron wave function without invoking degrees of freedom additional to nucleon ones.

In the article the questions of optimization of technological schemes of obtaining liquid carbon dioxide directed to the carbamide synthesis plant are considered. The main drawback of traditional technical solutions is high energy costs, mainly due to the need to compress CO2 before it is fed to the synthesis reactor. Traditionally, technical solutions are proposed, based on the production of liquid low-temperature carbon dioxide, which increase the yield of nitrogen fertilizer. However, their significant disadvantage is high energy costs, which is largely due to the need to compress CO2 before is fed to the synthesis reactor. To solve the optimization of the technological stage of obtaining high-pressure carbon dioxide by combining the use of compression and pumping equipment, multifactor methods for modelling chemical-technological processes and software were used. With regard to urea aggregates of different power, several technological schemes are considered. The paper presents a variant of modernization of the turbocharger aggregate, due to which it is possible to achieve a significant increase in the yield of the final product of urea units in order to reduce CO2 emissions into the atmosphere.

The tensor analyzing power T20 of the reaction d+A→π−(0°)+X has been measured in the fragmentation of 9 GeV tensor polarized deuterons into pions with momenta from 3.5 to 5.3 GeV/c on hydrogen, beryllium and carbon targets. This kinematic range corresponds to the region of cumulative hadron production with the cumulative variable xc from 1.08 to 1.76. The values of T20 have been found to be small and consistent with positive values. This contradicts the predictions based on a direct mechanism assuming NN collision between a high momentum nucleon in the deuteron and a target nucleon (NN→NNπ).

As part of its HL-LHC upgrade program, the CMS collaboration is replacing its existing endcap calorimeters with a high-granularity calorimeter (CE). The new calorimeter is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic and hadronic compartments. Due to its compactness, intrinsic time resolution, and radiation hardness, silicon has been chosen as active material for the regions exposed to higher radiation levels. The silicon sensors are fabricated as 20 cm (8") wide hexagonal wafers and are segmented into several hundred pads which are read out individually. As part of the sensor qualification strategy, 8" sensor irradiation with neutrons has been conducted at the Rhode Island Nuclear Science Center (RINSC) and followed by their electrical characterisation in 2020-21. The completion of this important milestone in the CE's R&D program is documented in this paper and it provides detailed account of the associated infrastructure and procedures. The results on the electrical properties of the irradiated CE silicon sensors are presented.

Experiment NA49 at the CERN SPS uses a large acceptance detector for a systematic study of particle yields and correlations in nucleus-nucleus, nucleon-nucleus and nucleon-nucleon collisions. Preliminary results for Pb+Pb collisions at 40, 80 and 158 A⋅GeV beam energy shown and compared to measurements at lower and higher energies.

Large modules of BaF2 crystals were tested with gamma sources and in beams of relativistic particles accelerated at the Dubna synchrophasotron. The energy resolution and the timing characteristics of BaF2 crystals depend on the strobe signals. A good uniformity of the light output along the whole length of the crystals when irradiated with relativistic particles and gamma-rays has been demonstrated.

New data on the tensor analyzing power Ayy of the ^9Be(d,p)X reaction at an initial deuteron momentum of 5 GeV/c and secondary particles (protons and deuterons) detection angle of 178 mr have been obtained at the JINR Synchrophasotron. The proton data obtained are analyzed within the framework of an approach based on the light-front dynamics using Karmanov's relativistic deuteron wave function. Contrary to the calculations with standard non-relativistic deuteron wave functions, we have managed to explain the new data within the framework of our approach without invoking degrees of freedom additional to nucleon ones. The ^9Be(d,d)X data are obtained in the vicinity of the excitation of baryonic resonances with masses up to 1.8 GeV/c^2. The Ayy data are in a good agreement with the previous data obtained at 4.5 and 5.5 GeV/c when they are plotted versus $t$. The results of the experiment are compared with the predictions of the plane wave impulse approximation and ω-meson exchange models.