Nuclear matter

Recent results from the PHENIX experiment on heavy flavors and quarkonia production in p + Al, p + Au, d + Au, and Au + Au collision systems at √ s NN = 200 GeV are summarized. The results are carried out by the measurements of the nuclear modification factors and elliptic flow. The nuclear modification factors measurements give insight into the energy loss of heavy quarks in the quark-gluon plasma medium along their path lengths. The elliptic flow measurements are a good tool to investigate the coupling of heavy quarks with the medium. The measurements are presented as a function of centrality, rapidity, and transverse momentum. The interpretations of the results in light of our current theoretical models, and comparison to LHCb and ALICE measurements are presented.

The three Υ states, Υ(1S+2S+3S), are measured in d+Au and p+p collisions at √ s N N =200 GeV and rapidities 1.2 < |y| < 2.2 by the PHENIX experiment at the Relativistic Heavy-Ion Collider. Cross sections for the inclusive Υ(1S+2S+3S) production are obtained. The inclusive yields per binary collision for d+Au collisions relative to those in p+p collisions (R dAu ) are found to be 0.62 ± 0.26 (stat) ± 0.13 (syst) in the gold-going direction and 0.91 ± 0.33 (stat) ± 0.16 (syst) in the deuteron-going direction. The measured results are compared to a nuclear-shadowing model, EPS09 [JHEP 04, 065 (2009)], combined with a final-state breakup cross section, σ br , and compared to lower energy p+A results. We also compare the results to the PHENIX J/ψ results [Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity dependence of the observed Υ suppression is consistent with lower energy p+A measurements.

Monte Carlo simulations with the CRISP code were conducted to study spallation and fission fragment distributions induced by intermediate-and high-energy protons and photons on actinide and pre-actinide nuclei. The model accounts for intranuclear cascade, pre-equilibrium, and evaporation-fission competition, enabling consistent treatment of both residues and fission products. Comparisons with experimental data show good agreement in mass and charge distributions, with minor deviations for light fragments. The results highlight the reliability of Monte Carlo approaches for predicting residual nuclei and fragment yields under accelerator-driven system (ADS) conditions. This work provides nuclear data relevant to ADS design, safety, and transmutation analysis

Neutron stars provide unique laboratories for studying matter under extreme conditions, from the outer atmosphere to the ultra-dense core. This review covers the formation of neutron stars in core-collapse supernovae and details their layered internal structure, including the atmosphere, envelope, crust, and dense nuclear core. We discuss key physical processes such as neutrino cooling, superfluidity, superconductivity, and the role of quantum condensates in shaping neutron star behavior. The interplay of superfluid vortices and magnetic flux tubes explains observed phenomena like pulsar glitches, while strong magnetic fields govern spin evolution and high-energy emission. Advances in mass and radius measurements from X-ray and gravitational-wave observations are constraining the equation of state of dense nuclear matter. By combining theoretical insights and observations, this work summarizes current knowledge of neutron star interiors and outlines future pathways for understanding matter at supranuclear densities.

We discuss the performances of a trigger implemented for the planned neutrino telescope NEMO. This trigger seems capable to discriminate between the signal and the strong background introduced by atmospheric muons and by the β decay of the 40 K nuclei present in the water. The performances of the trigger, as evaluated on simulated data are analyzed in detail.

We present a study of two-particle correlation functions involving photons and neutral pions in proton-proton and lead-lead collisions at the LHC energy. The aim is to use these correlation functions to quantify the effects of the medium on the jet decay properties.

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We carried out a statistical analysis of microglitch events on a sample of radio pulsars. The distributions of microglitch events in frequency (ν) and first frequency derivative (ν ) indicate that the size of a microglitch and sign combinations of events in ν and ν are purely randomized. Assuming that the probability of a given size of a microglitch event occurring scales inversely as the absolute size of the event in both ν and ν , we constructed a cumulative distribution function (CDF) for the absolute sizes of microglitches. In most of the pulsars, the theoretical CDF matched the observed values. This is an indication that microglitches in pulsar may be interpreted as an avalanche process in which angular momentum is transferred erratically from the flywheel-like superfluid interior to the slowly decelerating solid crust. Analysis of the waiting time indicates that it is purely Poisson distributed with mean microglitch rate γ ∼ 0.94 ± 0.25 year -1 for all the pulsars in our sample and T ∼ 1.26 ± 0.21 year giving γ / T ∼ 1.19 ± 0.27. Correlation analysis showed that the relative absolute size of microglitch event correlates with the rotation period of the pulsar with correlation coefficient r ∼ 0.7 and r ∼ 0.5 respectively for events in ν and ν . The mean glitch rate and number of microglitches (N g ) showed some dependence on spin down rate (r ∼ -0.6) and the characteristic age of the pulsar (τ ) with (r ∼ -0.4/-0.5).

Quasi-topological gravity is a new gravitational theory including curvature-cubed interactions and for which exact black hole solutions were constructed. In a holographic framework, classical quasi-topological gravity can be thought to be dual to the large N c limit of some non-supersymmetric but conformal gauge theory. We establish various elements of the AdS/CFT dictionary for this duality. This allows us to infer physical constraints on the couplings in the gravitational theory. Further we use holography to investigate hydrodynamic aspects of the dual gauge theory. In particular, we find that the minimum value of the shearviscosity-to-entropy-density ratio for this model is η/s ≃ 0.4140/(4π).

GeV) will be relayed. The approach is to follow the procedure developed in earlier p+p and d+Au analyses. Neutral pions are reconstructed from decay photons that strike the MPC.The position of reconstructed neutral pion mass peaks are compared to those expected from a perfectly calibrated detector (as determined by simulation) adjusting the gains of each calorimeter tower until the data are brought into agreement with the simulation.In the past, these calibrations have utilized the Pythia event generator to calibrate p+p and d+Au data. In the case of these heavy ion data, initially, peripheral collisions will be compared to the Pythia p+p results, but eventually, Hijing will be used to calibrate the Au+Au data. 1 We gratefully acknowledge support from the NSF Grant Number 1209240

Recent developments in obtaining a detailed model for gamma ray bursts have shown the need for a deeper understanding of phenomena described by solutions of the Einstein-Maxwell equations, reviving interest in the behavior of charges close to a black hole. In particular a drastic difference has been found between the lines of force of a charged test particle in the fields of Schwarzschild and Reissner-Nordström black holes. This difference characterizes a general relativistic effect for the electric field of a charged test particle around a (charged) Reissner-Nordström black hole similar to the "Meissner effect" for a magnetic field around a superconductor. These new results are related to earlier work by Fermi and Hanni-Ruffini-Wheeler.

Данная статья является теоретическим разделом и продолжением статьи: «Периодическая система изотопов», в которой была выполнена проверка системы на соответствие по 10 типам экспериментальных данных, обнаружено периодическое изменение свойств на уровне ядер и вертикальная симметрия подгрупп изотопов. Периодическая система изотопов построена с помощью, специального алгоритмапринципа многоуровневой периодичности атома, от электронов к ядру. В качестве описания многоуровневой периодичности, в данной статье представлена единая система квантовых чисел, с помощью которой выполнено описание, как оболочек электронов, так и нуклонов (биномальная вероятностная интерпретация). С помощью биномальной интерпретации решена задача о частице в одномерной потенциальной яме, выполнен квантовомеханический расчет для функций вероятности орбиталей и периодов, как электронов, так и нуклонов,получены характеристические уравнения, воспроизведены проекции электронных орбиталей, показано соответствие биномальной интерпретации семейству сферических гармоник. Для орбиталей электронов выполнен расчет и анализ решений уравнения Шредингера для биномальной интерпретации квантовых чисел. Показана пространственная природа квантовых чисел, для данной интерпретации, в виде степеней свободы. На основе принципа многоуровневой периодичности выведены выражения и выполнены построения плоских проекций орбиталей нуклонов ядра, сделан анализ и выявлено подобие форм с орбиталями электронов. Сделан критический анализ современной сферической системы координат, показаны возможные ошибки в построении орбиталей электронов, с учетом недостатков, предложены две альтернативные сферические системы координат, для которых произведен расчет коэффициентов Ламе и выведены уравнения Лапласа. В качестве поиска фундаментальной причины многоуровневой периодичности, представлена пространственная модель с изменяющимися степенями свободы 0-n, найдено её проявление в природе (формы кристаллов); предложен ряд экспериментов; высказаны прогнозы о применимости принципа многоуровневой периодичности в кварковой теории. Тематика данной статьи лежит в области задач объединения сильного и электромагнитного взаимодействий.

We explore the relevance of confinement in quark matter models for the possible quark core of neutron stars. For the quark phase, we adopt the equation of state (EoS) derived with the Field Correlator Method, extended to the zero temperature limit. For the hadronic phase, we use the microscopic Brueckner-Hartree-Fock many-body theory. We find that the currently adopted value of the gluon condensate G2 ≃ 0.006-0.007 GeV 4 , which gives a critical temperature Tc ≃ 170 MeV, produces maximum masses which are only marginally consistent with the observational limit, while larger masses are possible if the gluon condensate is increased.

We identify the dual geometry of the hadron phase of dense nuclear matter and investigate the confinement/deconfinement phase transition. We suggest that the low temperature phase of the RN black hole with the full backreaction of the bulk gauge field is described by the zero mass limit of the RN black hole with hard wall. We calculated the density dependence of critical temperature and found that the phase diagram closes. We also study the density dependence of the ρ meson mass.

Ultrarelativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) are thought to have produced a state of matter called the Quark-Gluon-Plasma (QGP). The QGP forms when nuclear matter governed by Quantum Chromodynamics (QCD) reaches a temperature and baryochemical potential necessary to achieve the transition of hadrons (bound states of quarks and gluons) to deconfined quarks and gluons. Such conditions have been achieved at RHIC, and the resulting QGP created exhibits properties of a near perfect fluid. In particular, strong evidence shows that the QGP exhibits a very small shear viscosity to entropy density ratio η/s, near the lower bound predicted for that quantity by Anti-deSitter space/Conformal Field Theory (AdS/CFT) methods of η/s = 4πk B , where is Planck's constant and k B is Boltzmann's constant. As the produced matter expands and cools, it evolves through a phase described by a hadron gas with rapidly increasing η/s. This thesis presents robust calculations of η/s for hadronic and partonic media as a function of temperature using the Green-Kubo formalism. An analysis is performed for the behavior of η/s to mimic situations of the hadronic media at RHIC evolving out of chemical equilibrium, and systematic uncertainties are assessed for our method. In addition, preliminary results are presented for the bulk viscosity to entropy density ratio ζ/s, whose behavior is not well-known in a relativistic heavy ion collisions. The diffusion coefficient for baryon number is investigated, and an algorithm is presented to improve upon the previous work of investigation of heavy quark diffusion in a iv thermal QGP. By combining the results of my investigations for η/s from our microscopic transport models with what is currently known from the experimental results on elliptic flow from RHIC, I find that the trajectory of η/s in a heavy ion collision has a rich structure, especially near the deconfinement transition temperature T c . I have helped quantify the viscous hadronic effects to enable investigators to constrain the value of η/s for the QGP created at RHIC. v To Soliman M. Demir, who shall always be remembered in our lives. vi

A novel Hadron Blind Detector (HBD) has been developed for an upgrade of the PHENIX experiment at RHIC. The HBD will allow a precise measurement of electronpositron pairs from the decay of the light vector mesons and the low-mass pair continuum in heavy-ion collisions. The detector consists of a 50 cm long radiator filled with pure CF 4 and directly coupled in a windowless configuration to a triple Gas Electron Multiplier (GEM) detector with a CsI photocathode evaporated on the top face of the first GEM foil.

We obtain posterior distribution of equations of state (EOSs) across a broad range of density by imposing explicitly the constraints from precisely measured fundamental properties of finite nuclei, in combination with the experimental data from heavy-ion collisions and the astrophysical observations of radius, tidal deformability and minimum-maximum mass of neutron stars. The acquired EOSs exhibit a distinct global behavior compared to those usually obtained by imposing the finite nuclei constraints implicitly through empirical values of selected key parameters describing symmetric nuclear matter and symmetry energy in the vicinity of the saturation density. The explicit treatment of finite nuclei constraints yields softer EOSs at low densities which eventually become stiffer to meet the maximum mass criteria. The Kullback-Leibler divergence has been used to perform a quantitative comparison of the distributions of neutron star properties resulting from the EOSs obtained from implicit and explicit finite nuclei constraints.

We suggest a mechanism that may resolve a conflict between the precession of a neutron star and the widely accepted idea that protons in the bulk of the neutron star form a type-II superconductor. We will show that if there is a persistent, non-dissipating current running along the magnetic flux tubes the force between magnetic flux tubes may be attractive, resulting in a type-I, rather than a type-II, superconductor. If this is the case, the conflict between the observed precession and the canonical estimation of the Landau-Ginzburg parameter κ > 1/ √ 2 (which suggests type-II behaviour) will automatically be resolved. We calculate the interaction between two vortices, each carrying a current j, and demonstrate that when j > c 2qλ , where q is the charge of the Cooper pair and λ is the Meissner penetration depth, a superconductor is always type-I, even when the cannonical Landau-Ginzburg parameter κ indicates type-II behaviour. If this condition is met, the magnetic field is completely expelled from the superconducting regions of the neutron star. This leads to the formation of the intermediate state, where alternating domains of superconducting matter and normal matter coexist. We further argue that even when the induced current is small j < c 2qλ the vortex Abrikosov lattice will nevertheless be destroyed due to the helical instability studied previously in many condensed matter systems. This would also resolve the apparent contradiction with the precession of the neutron stars. We also discuss some instances where anomalous induced currents may play a crucial role, such as in neutron star kicks, pulsar glitches, the toroidal magnetic field and the magnetic helicity.

To elucidate the observable distinctions between different reaction mechanisms for multifragment production in nuclear collisions at intermediate energies, we contrast two opposite extremes: sequential binary fission and simultaneous multifragment breakup (true multifragmentation). For identical multifragment channels produced by these two idealized mechanisms, we examine the kinetic-energy spectra and the correlated velocity distributions of the fragments and discuss the possibility of identifying informative multifragment observables .

We present a summary of on-going calculations that address the static and dynamic structure of nuclear matter. Specific projects include (i) evaluation of the density-density response function and corresponding dynamic structure factor, based on the correlated random-phase approximation (CRPA_I) and generalizations of this method, and (ii) low-order variational calculation of the reduced two-body density matrix and corresponding generalized momentum distribution. The numerical applications involve the model interaction V2.

We study the Thirring model in three spacetime dimensions, by means of Monte Carlo simulation on lattice sizes 8 3 and 12 3 , for numbers of fermion flavors N f = 2, 4, 6. For sufficiently strong interaction strength, we find that spontaneous chiral symmetry breaking occurs for N f = 2, 4, in accordance with the predictions of the Schwinger-Dyson approach. The phase transitions which occur are continuous and with critical scaling behaviour depending on N f . For N f = 6 our results are preliminary, and no firm conclusions about the existence or otherwise of chiral symmetry breaking are possible.

I review dynamical chiral symmetry breaking in four-fermi models, including results of Monte Carlo simulations with dynamical fermions. For 2 < d < 4, where the phase transition defines an ultraviolet fixed point of the renormalisation group, the continuum theory may either be describable using the large-N f expansion, as in the case of the Gross-Neveu model, or be intrinsically non-perturbative, as in the case of the Thirring model. For d = 4, the models are trivial and are described by a mean field equation of state with logarithmic corrections to scaling, which may nonetheless define new universality classes distinct from those of ferromagnetism.

We present the first official release of the nCTEQ nuclear parton distribution functions with errors. The main addition to the previous nCTEQ PDFs is the introduction of PDF uncertainties based on the Hessian method. Another important addition is the inclusion of pion production data from RHIC that give us a handle on constraining the gluon PDF. This contribution summarizes our results from [1] and concentrates on the comparison with other groups providing nuclear parton distributions.

A high-sensitivity search for the strangeness S 22 H dibaryon ͑uuddss͒ was conducted at the Brookhaven Alternating Gradient Synchrotron (AGS) using the reaction 3 He͑K 2 , K 1 ͒Hn at P K 2 1.8 GeV͞c. The sensitivity was independent of H lifetime and decay modes. No evidence for H production was observed. In a mass range extending from about 50 to 380 MeV͞c 2 below the LL threshold of 2.231 GeV͞c 2 , the resulting upper limits on the H-production cross section are in the range of 0.058 to 0.021 mb͞sr, approximately 1 order of magnitude below a theoretical calculation. [S0031-9007(97)

Strange quark matter made of up, down and strange quarks has been postulated by Witten . Strange quark matter would be nearly charge neutral and would have density of nuclear matter (10 14 gm/cm 3 ). Witten also suggested that nuggets of strange quark matter, or strange quark nuggets (SQNs), could have formed shortly after the Big Bang, and that they would be viable candidates for cold dark matter. As suggested by de Rujula and Glashow [2], an SQN may pass through a celestial body releasing detectable seismic energy along a straight line. The Moon, being much quieter seismically than the Earth, would be a favorable place to search for such events. We review previous searches for SQNs to illustrate the parameter space explored by using the Moon as a low-noise detector of SQNs. We also discuss possible detection schemes using a single seismometer, and using an International Lunar Seismic Network.

Starting with the previous result that the equation of motion for some collective motion of the nuclear fluid can be approximated by the Lame equation, we consider the nuclear giant resonances as elastic vibrations of a nucleus, the properties of elasticity being a peculiar manifestation of the quantum stress tensor. The nucleus is taken to be compres- sible and endowed with elastic moduli, surface tension, Coulombic charge, and two-body viscosity. Eigenenergles and widths for the isoscalar electric multipole states (0+, 1, 2+, 3, 4+, . . . ) and the isoscalar magnetic multipoles states (1+,2, 3+, 4, . . . ) are obtained. The energies and widths of the 0+, 2+, and 3 states agree well with those of the observed giant resonances. Such agreement lends support to the present macro- scopic description of the collective excitation of a nucleus. Nuclear viscosity coeAicients and the incompressibility of nuclear matter are extracted. In the present unified ap- proach, the high-lying electric multipole "giant resonance" states and the low-lying "liquid-drop" states emerge as eigenstates of the same characteristic equation. Similari- ties and differences-between these two types of states are assessed. NUCLEAR STRUCTURE Giant resonances vibration of a compres- sible, elastic sphere with surface tension, charge, and viscosity. Electric multipole and magnetic multipole resonances. Nuclear viscosity coeffi- cients and incompressibility extracted.

With the HADES spectrometer at GSI we have studied dilepton production in various collision systems from elementary N + N , over p + A , up to the medium-heavy Ar + KCl system. We have confirmed the puzzling results of the former DLS collaboration at the Bevalac. While we have traced the origin of the excess pair yield in C + C collisions to elementary p + p and n + p processes, we find a significant contribution from the dense phase of the collision in larger Ar + KCl system. From recently obtained e + e - pair spectra in p + p and p + Nb interactions at 3.5 GeV kinetic beam energy the inclusive production cross sections for neutral pions, η , ω and ρ mesons are extracted for the first time at this beam energy. Furthermore, the production mechanisms of the vector mesons, which are not known at these energies, are investigated. The direct comparison of p + p and p + Nb data allows us to investigate in-medium mass modifications of vector mesons at nuclear ground state density. On the...

Recent data on isoscalar giant monopole resonance (ISGMR) in the calcium isotopes 40,44,48 Ca have suggested that K τ , the asymmetry term in the nuclear incompressibility, has a positive value. A value of K τ > 0 is entirely incompatible with present theoretical frameworks and, if correct, would have far-reaching implications on our understanding of myriad nuclear and astrophysical phenomena. This paper presents results of an independent ISGMR measurement with the 40,42,44,48 Ca(α, α ) reaction at E α = 386 MeV. These results conclusively discount the possibility of a positive value for K τ , and are consistent with the previously-obtained values for this quantity.

The isoscalar giant dipole resonnace (ISGDR) has been investigated in 208 Pb using inelastic scattering of 400 MeV α particles at extremely forward angles, including 0 • . Using the superior capabilities of the Grand Raiden spectrometer, it has been possible to obtain inelastic spectra devoid of any "instrumental" background. The ISGDR strength distribution has been extracted from a multipole-decomposition of the observed spectra. The implications of these results on the experimental value of nuclear incompressibility are discussed.

The strength distributions of the giant monopole resonance (GMR) have been measured in the even-A Sn isotopes (A=112-124) with inelastic scattering of 400-MeV α particles in the angular range 0 • -8.5 • . We find that the experimentally-observed GMR energies of the Sn isotopes are lower than the values predicted by theoretical calculations that reproduce the GMR energies in 208 Pb and 90 Zr very well. From the GMR data, a value of K τ = -550 ± 100 MeV is obtained for the asymmetry-term in the nuclear incompressibility.

The isoscalar giant dipole resonance (ISGDR) in 208 Pb has been investigated using inelastic scattering of 200 MeV a particles at and near 0 ± where the angular distribution of the ISGDR can be clearly differentiated from those of other modes. The "difference of spectra" technique was employed to separate the ISGDR from the high-energy octupole resonance (HEOR). These data provide the clearest evidence yet for the ISGDR adjacent to the HEOR. With these results, all expected isoscalar l # 3 resonances in 208 Pb have been identified. [S0031-9007(97)03674-0]

The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for γp → φp, γd → φpn and γd → φd at forward production angles. A linearly polarized photon beam at E γ = 1.6 -2.4 GeV was used for the production of φ mesons. The natural-parity Pomeron exchange processes remain dominant near threshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from the nucleons but is greatly reduced in the coherent production from deuterons. There is no strong E γ dependence, but there is some dependence on momentum transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the t-channel is observed.

The systematic behavior of the isoscalar giant dipole resonance (ISGDR) in 90 Zr, 116 Sn, 144 Sm, and 208 Pb is studied with inelastic ␣ scattering at E ␣ = 386 MeV. Multipole-decomposition analysis is applied to extract the excitation strengths of giant resonances from the ͑␣ , ␣Ј͒ differential cross sections at lab = 0.64°-13.5°. The bimodal structure of the ISGDR is discussed and compared with recent theoretical results from Hartree-Fock+ random-phase-approximation calculations.

We have investigated the isoscalar giant resonances in the Sn isotopes using inelastic scattering of 386-MeV α-particles at extremely forward angles, including 0 • . We have obtained completely "background-free" inelastic-scattering spectra for the Sn isotopes over the angular range 0 • -9 • and up to an excitation energy of 31.5 MeV. The strength distributions for various multipoles were extracted by a multipole decomposition analysis based on the expected angular distributions of the respective multipoles. We find that the centroid energies of the isoscalar giant monopole resonance (ISGMR) in the Sn isotopes are significantly lower than the theoretical predictions. In addition, based on the ISGMR results, a value of K τ = -550 ± 100 MeV is obtained for the asymmetry term in the nuclear incompressibility. Constraints on interactions employed in nuclear structure calculations are discussed on the basis of the experimentally-obtained values for K ∞ and K τ .

Submitted for the DNP06 Meeting of The American Physical Society Compressional-mode Giant Resonances in 24 Mg. 1 P.V. MAD-HUSUDHANA RAO, T. LI, B.K. NAYAK, U. GARG, Physics Department, University of Notre Dame, Notre Dame, IN 46556, USA, M. ITOH, M. YOSOI, M. UCHIDA, H. TAKEDA, Y. YASUDA, H.

A measurement of the ratio R c ¼ ð c ! J=c þ Þ=J=c in pC, pTi, and pW interactions at 920 GeV=c ( ffiffi ffi s p ¼ 41:6 GeV) in the Feynman-x range À0:35 < x J=c F < 0:15 is presented. Both þ À and e þ e À J=c decay channels are observed with an overall statistics of about 15 000 c events, which is by far the largest available sample in pA collisions. The result is R c ¼ 0:188 AE 0:013 st þ0:024 À0:022sys averaged over the different materials, when no J=c and c polarizations are considered. The c1 to c2 production ratio R 12 ¼ R c 1 =R c 2 is measured to be 1:02 AE 0:40, leading to a cross section ratio ð c1 Þ ð c2 Þ ¼ 0:57 AE 0:23. The dependence of R c on the Feynman-x of the J=c , x J=c F , and its transverse momentum, p J=c T , is studied, as well as its dependence on the atomic number, A, of the target. For the first time, an extensive study of possible biases on R c and R 12 due to the dependence of acceptance on the polarization states of J=c and c is performed. By varying the polarization parameter, obs , of all produced J=c 's by two sigma around the value measured by HERA-B, and considering the maximum variation due to the possible c1 and c2 polarizations, it is shown that R c could change by a factor between 1.02 and 1.21 and R 12 by a factor between 0.89 and 1.16.

Ratios of the ψ ′ over the J/ψ production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The ψ ′ and J/ψ states were reconstructed in both the µ + µ -and the e + e -decay modes. The measurements covered the kinematic range -0.35 ≤ xF ≤ 0.1 with transverse momentum pT ≤ 4.5 GeV/c. The ψ ′ to J/ψ production ratio is almost constant in the covered xF range and shows a slow increase with pT . The angular dependence of the ratio has been used to measure the difference of the ψ ′ and J/ψ polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is R ψ ′ (µ)/R ψ ′ (e) = 1.00 ± 0.08 ± 0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B ′ (µ) • B(e)) / (B(µ) • B ′ (e)), of ψ ′ and J/ψ in the two channels.

Measurements of the kinematic distributions of J /ψ mesons produced in p-C, p-Ti and p-W collisions at √ s = 41.6 GeV in the Feynman-x region -0.34 < x F < 0.14 and for transverse momentum up to p T = 5.4 GeV/c are presented. The x F and p T dependencies of the nuclear suppression parameter, α, are also given. The results are based on 2.4 × 10 5 J /ψ mesons reconstructed in both the e + e -and μ + μ -decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of x F for the first time. The average value of α in the measured x F region is 0.981 ± 0.015. The data suggest that the strong nuclear suppression of J /ψ production previously observed at high x F turns into an enhancement at negative x F .

Inclusive differential cross sections dσ pA /dx F and dσ pA /dp 2 t for the production of K 0 S , Λ, and Λ particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to √ s = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dσ pA (K 0 S )/dσ pA (Λ) and dσ pA ( Λ)/dσ pA (Λ) are measured to be 6.2 ± 0.5 and 0.66 ± 0.07, respectively, for x F ≈ -0.06. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions dσ pA /dp 2 t also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections σ pA on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon σ pN are compared with results obtained at other energies.