Search

The global α -nucleus optical model is studied based on the nucleon self-energies in an Dirac-Brueckner-Hartree-Fock (DBHF) approach. The newly developed nucleon-nucleus optical model CTOM derived from DBHF, is used as the basis to consistently generate the real and imaginary potentials of the α -nucleus optical potential by double-folding model. The same range correction a of the improved local density approximation (ILDA) in CTOM is adopted, which is also suitable to modify the nucleon interaction range in α -nucleus systems. To get better description of experimental data, the re-normalization factors ( N R , N I ) are introduced in α -nucleus scattering calculations, and the individual optimized ( N R , N I ) for all nuclei and energies are searched out under the guidance of χ 2 criterion. We systematically explore the energy dependence of N R and N I by considering the α elastic scattering from 12 C to 208 Pb at incident energies below 120 MeV / nucleon and a simple exponential function is extracted. With this global α -nucleus optical potential, a reasonable description of all available experimental data for α scattering from nuclei is achieved.

Nonlocal effects result in complications when predicting scattering observables. This is usually seen when one analyses the data for nucleon scattering off light 1p-shell nuclei using local optical model potentials. In this work we employ the nonlocal optical model of Perey and Buck (1962) [10] to study the neutron-light nucleus scattering process. By fitting the individual elastic angular distributions we determine energy-dependent, target-specific potential parameters. Then, for each nucleus, a constant set of nonlocal parameters is obtained by simultaneously fitting the corresponding elastic angular distributions. The good quality of the fits prompted us to search for a global constant set of nonlocal parameters by simultaneously fitting a large number elastic angular distribution sets for neutron scattering off light nuclei from 6Li to 18O over the energy range 9 to 35 MeV. We also show that the implicit inclusion of nonlocality in the optical model does not fully remove the need for energy-dependent potential parameters. This is achieved by expressing the nonlocal imaginary volume and surface depths of the constant global set as linear functions of energy and the asymmetry term. The effectiveness of this set is tested by applying it to additional light nuclei and energies outside the fitted range. The predicted elastic angular distributions compared well with the measured data.

Absolute differential cross sections for elastic $p^7$Be and $p^8$B small-angle scattering were measured in inverse kinematics at an energy of 0.7 GeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR was used as an active target to detect the recoil protons. The projectile tracking and isotope identification were performed with multi-wire proportional chambers and scintillation detectors. The measured cross sections were analysed using the Glauber multiple-scattering theory. The root-mean-square (rms) nuclear matter radii $R_{\rm m} = 2.42 (4)$ fm for $^7$Be and $R_{\rm m} = 2.58 (6)$ fm for $^8$B were obtained. The radial density distribution deduced for $^8$B exhibits a proton halo structure with the rms halo radius $R_{\rm h} = 4.24 (25)$ fm. A comparison of the deduced experimental radii is displayed with existing experimental and theoretical data., 18 pages, 6 figures. arXiv admin note: text overlap with arXiv:1803.02044

To investigate the breakup coupling effects on the formation of the nuclear rainbow, the existing experimental data of the refractive elastic scattering of 6Li on 12C, 40Ca, 58Ni and 90Zr targets at 35 AMeV are analyzed. The continuum discretized coupled-channel (CDCC) method is adopted to calculate the elastic scattering angular distributions including the coupling effects from the breakup of 6Li into α and d. The one-channel (1-ch) calculations that switch off the breakup coupling are also performed for comparison. In the calculated angular distributions given by both approaches, the first Airy (A1) minimum shows a trend of moving to larger angles as the target mass increases. Comparing the calculated results through two approaches, one can find that the breakup coupling shifts the A1 minima to larger angles. This shows that the breakup coupling can boost the nuclear rainbow, although it also damps the elastic scattering cross sections. We also find that the stronger the breakup coupling is, the larger the A1 shift becomes.

We present a new calculation of the Li 6 ( p , γ ) 7 Be radiative capture astrophysical S-factor in a cluster model framework. We consider several intercluster potentials, adjusted to reproduce the Be 7 bound state properties and the p − 6 Li elastic scattering phase shifts. Using these potentials, we calculate the astrophysical S-factor, obtaining a good agreement with available data, and the photon angular distribution. Finally, we discuss the consequences of a hypothetical resonance-like structure on the S-factor.

The systematic approach to calculating cross section of inelastic neutron scattering on 6Li and 7Li nuclei in the range of kinetic energies E n = 0.1 − 20 MeV is presented. The reaction mechanism is described using the Faddeev equations within the problem of neutron interaction with two clusters which form the target nucleus bound state. The length a n Li of elastic n−Li scattering are calculated. The coherence effect on n 5 Li and αd contributions to 6Li nucleus ground state is demonstrated by the example of elastic neutron scattering reaction. Total and differential cross sections of inelastic neutron scattering on 6Li and 7Li nuclei with formation of three and four particles in the final state are calculated. Three-body interaction of clusters which form the target nucleus ground state in 6Li ( n , n ′ ) d α and 7Li ( n , n ′ α ) t reactions is shown to be of great importance.

We perform a parameter-free calculation for the high-energy proton-nucleus scattering based on the Glauber theory. A complete evaluation of the so-called Glauber amplitude is made by using the factorization of the single-particle wave functions. The multiple-scattering or multistep processes are fully taken into account within the Glauber theory. We demonstrate that proton- $^{12}$C, $^{20}$Ne, and $^{28}$Si elastic and inelastic scattering ($J^\pi=0^+ \to 2^+$ and $0^+ \to 4^+$) processes are very well described in a wide range of the incident energies from $\sim$50 MeV to $\sim$ 1 GeV. We evaluate the validity of a simple one-step approximation andfind that the approximation works fairly well for the inelastic $0^+ \to 2^+$ processes but not for $0^+ \to 4^+$ where the multistep processes become more important. As an application, we quantify the difference between the total reaction and interaction cross sections of proton-$^{12}$C, $^{20}$Ne, and $^{28}$Si collisions., Comment: 29 pages, 6 figures, to appear in Nucl. Phys. A

Evidence for light-by-light (LbL) scattering, gamma gamma -> gamma gamma, in ultraperipheral PbPb collisions at a nucleon-nucleon center of-mass energy of 5.02 TeV is reported. LbL scattering processes are selected in events with just two photons produced, with transverse energy E-T(gamma) > 2 GeV, pseudorapidity vertical bar eta(gamma)vertical bar 5 GeV, transverse momentum p(T)(gamma gamma) gamma gamma) = 122 +/- 46 (stat) +/- 29 (syst) +/- 4 (theo) nb is consistent with the standard model prediction.

Jets produced at a future electron-ion collider (EIC) are predominantly initiated by energetic quarks, and the subsequent branching of these quarks into systems of quarks and gluons is heavily modified by multiple scattering in the nuclear medium. In cold nuclear matter and in the quark-gluon plasma, this feature allows jet cross sections and jet substructure to be used as a probe of the medium's properties. Here we present a formalism for computing the gluon substructure of a quark jet to an arbitrary order in opacity, the average number of scatterings in the medium, while maintaining the exact kinematics of the splitting. We present explicit results at second order in opacity for the first time, along with a recursion relation which can be used to construct the solution for arbitrarily high orders in opacity. The theoretical framework demonstrated here applies equally well to light and heavy quark branching, and is easily generalizable to other systems.

In a quantum field theory, apparent thermalization can be a consequence of entanglement as opposed to scatterings. We discuss here how this can help to explain open puzzles such as the success of thermal models in electron-positron collisions. It turns out that an expanding relativistic string described by the Schwinger model (which also underlies the Lund model) has at early times an entanglement entropy that is extensive in rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature $T_\tau=\hbar/(2\pi k_B\tau)$, even in the absence of any scatterings., Comment: Contribution to the proceedings of Quark Matter 2018, to appear in Nuclear Physics A

Hidden charm mesons continue playing an essential role as relevant probes to understand the evolution of partonic matter. It is expected that the charmonia that survived the quark-gluon plasma phase suffer collisions with other particles composing the hadronic matter. In this work, we intend to contribute on this subject by presenting an updated study about the interactions of $J/\psi$ with surrounding hadronic medium. The meson-meson interactions are described with a $SU(4)$ effective Lagrangian, and within the framework of unitarized coupled channel amplitudes projected onto s-wave. The symmetry is explicitly broken to $SU(3)$ by suppression of the interactions driven by charmed mesons. We calculate the cross sections for $J/\psi $ scattering by light pseudoscalar mesons ($\pi, K, \eta$) and vector mesons ($\rho, K^\ast, \omega$), as well as their inverse processes. Keeping the validity of this present approach in the low CM energy range, the most relevant channels are evaluated and a comparison of the findings with existing literature is performed., Comment: 21 pages, 11 figures

The vector and tensor analysing powers in deuteron-proton elastic scattering have been measured in the forward hemisphere at deuteron kinetic energies of 1.2 GeV and 2.27 GeV using the ANKE spectrometer at the COSY storage ring. The results are compared with other experimental data and with predictions made within the framework of Glauber multiple scattering theory., Comment: 11 pages with 8 figures. To be submitted for publication

Differential cross sections and polarization correlations for the scattering of relativistic spin-polarized leptons from unpolarized ground-state sodium nuclei are calculated within the distorted-wave Born approximation (DWBA). Various nuclear ground-state charge distributions are probed. Besides potential scattering, also electric C2 and magnetic M1 and M3 transitions are taken into account. It is shown that even for a light nucleus such as 23Na there are considerable electron–positron differences at high collision energies and large scattering angles. In particular, the symmetry of the Sherman function with respect to a global sign change, as predicted by the second-order Born approximation when replacing electrons by positrons, is broken whenever the diffraction structures come into play beyond 100 MeV.

Measurements of neutron elastic and inelastic scattering cross sections from 54Fe were performed for nine incident neutron energies between 2 and 6 MeV. Measured differential scattering cross sections are compared to those from previous measurements and the ENDF, JENDL, and JEFF data evaluations. TALYS calculations were performed and modifications of the default parameters are found to better describe the experimental cross sections. A spherical optical model treatment is generally adequate to describe the cross sections in this energy region; however, in 54Fe the direct coupling is found to increase suddenly above 4 MeV and requires an increase in the DWBA deformation parameter by approximately 25%. This has little effect on the elastic scattering differential cross sections but makes a significant improvement in both the strength and shape of the inelastic scattering angular distribution, which are found to be very sensitive to the size and extent of the surface absorption region.

Within a nonlinear relativistic Hartree–Fock approximation combined with the BCS method, we study the effect of the nucleon–nucleon tensor force of the π -exchange potential on the spin- and pseudospin–orbit doublets along the Ca and Sn isotopic chains. We show how the self-consistent tensor force effect modifies the splitting of both kinds of doublets in an interdependent form, leading, quite generally, to opposite effects in the accomplishment of the spin and pseudospin symmetries (the one is restored, the other one deteriorates and vice versa). The ordering of the single-particle energy levels is crucial to this respect. Also, we observe a mutual dependence on the evolution of the shell closure gap Z = 50 and the energy band outside the core, along the Sn chain, as due to the tensor force. In fact, when the shell gap is quenched the outside energy band is enlarged, and vice versa. A reduction of the strength of the pion tensor force with respect to its experimental value from the nucleon–nucleon scattering is needed to get results closer to the experiment. Pairing correlations act to some extent in the opposite direction of the tensor term of the one-pion-exchange force.

We investigate properties of bound and resonance states in the Λ 9 Be nucleus. To reveal the nature of these states, we use a three-cluster 2 α + Λ microscopic model. The model incorporates Gaussian and oscillator basis functions and reduces a three-cluster Schrodinger equation to a two-body like many-channel problem with the two-cluster subsystems ( Λ 5 He and 8Be) being in a bound or a pseudo-bound state. Influence of the cluster polarization on the energy and widths of resonance states in Λ 9 Be and on elastic and inelastic Λ 5 He +α scattering is analyzed.

The O (g.s.) 16 + 8 Be (g.s.) structure of the ground state of 24Mg nucleus has been probed experimentally using direct knockout reaction Mg 24 ( O 16 , 2 16 O ) 8 Be in the quasi free scattering kinematics domain. The direct 16O-cluster knockout finite range prediction indicates a fair amount of O (g.s.) 16 + 8 Be (g.s.) component in the Mg (g.s.) 24 .

Within the framework of the modified potential cluster model with the classification of orbital states according to Young diagrams, the possibility of description experimental data for S-factor of the proton radiative capture on 7Li to the ground state of 8Be is considered. It was shown that taking into account E1 and M1 transitions from the state of p 7 Li scattering to the ground state of 8Be in the p 7 Li channel it is possible to explain the value of the S-factor at energies up to 10 MeV. Based on the calculated total cross sections, the reaction rate in the temperature range of 0.01 to 10.0 T 9 is obtained. It is demonstrated that the inclusion of low-lying resonance states gives some contribution into the reaction rate at high temperatures.

The probable role of the sudden nuclear charge change and nuclear recoil in the shaking processes during the neutron- or heavy-ion-induced nuclear reactions and weakly interacting massive particle–nucleus scattering has been investigated in the present work. Using hydrogenic wavefunctions, general analytical expressions of survival, shakeup/shakedown, and shakeoff probability have been derived for various subshells of hydrogen-like atomic systems. These expressions are employed to calculate the shaking, shakeup/shakedown, and shakeoff probabilities in some important cases of interest in the nuclear astrophysics and the dark matter search experiments. The results underline that the shaking processes are one of the probable channels of electronic transitions during the weakly interacting massive particle–nucleus scattering, which can be used to probe the dark matter in the sub-GeV regime. Further, it is found that the shaking processes initiating due to nuclear charge change and nuclear recoil during the nuclear reactions may influence the electronic configuration of the participating atomic systems and thus may affect the nuclear reaction measurements at astrophysically relevant energies.

Current pQCD calculations for the energy loss of a hard parton moving through a medium of thermalized static scattering centres are inapplicable to the small colliding systems (such as p / d + A ) that have, in recent years, hinted at the presence of tiny droplets of QGP through the presence of collective behaviour, strangeness enhancement and quarkonium suppression. The well-known DGLV, ASW, BDMPS-Z, AMY and HT calculations all exploit both the large separation distance (between scattering centre and radiation) and the large system approximations. We relax the large system assumption and recompute the energy loss in the DGLV formalism in order to address the glaring lack of theoretical control over small-system energy loss. Alarmingly, we find that the correction terms dominate at large energies, resulting in ∼ 100% negative correction, calling into question the validity of the large formation time assumption used in all pQCD-based energy loss calculations. Our results demand a complete overhaul of energy-loss calculations for all system sizes.

The p p ¯ invariant mass spectra of the processes J / ψ → p p ¯ ω , J / ψ → p p ¯ ρ , and J / ψ → p p ¯ γ close to the p p ¯ threshold are calculated by means of the N N ¯ optical potential. The potential model for N N ¯ interaction in the S 0 1 state is proposed. The parameters of the model are obtained by fitting the cross section of N N ¯ scattering together with the p p ¯ invariant mass spectra of the J / ψ decays. Good agreement with the available experimental data is achieved. Using our potential and the Green's function approach we also describe the peak in the η ′ π + π − invariant mass spectrum in the decay J / ψ → γ η ′ π + π − in the energy region near the N N ¯ threshold.

The refractive scattering of 17F+12C is analyzed systematically by using the optical model with the cluster folding potentials. First of all, the applicability of the cluster folding approach is validated by analyzing the elastic scattering data of 13C+12C and 12C+12C at 20 A MeV. To perform the optical model calculations of 17F+12C, the less ambiguous optical potentials of 16O+12C and the global optical potential of p+12C are used to give the cluster folding potentials. Apart from the reproduction of the experimental data of the elastic scattering of 17F+12C at 10 A MeV, the Airy patterns are noticeable from about 10 to 40 A MeV. For comparison, the optical model calculations of 17O+12C at the same energies per nucleon are also performed through the cluster folding approach, of which the results are very similar to those of 17F+12C. For both 17F+12C and 17O+12C, the energy dependence of the Airy minima is extracted and compared with that in the case of 16O+12C. It is found that the Airy minima characteristic of 17F+12C is nearly identical with that of 17O+12C and similar to that of 16O+12C, which indicates the strong contributions from the 16O core to the appearance of the nuclear rainbow effects in 17F scattering. At last, the calculated total reaction cross sections are compared with the strong absorption model, which verifies the reasonableness of the present optical model calculations.

The absolute differential cross sections for small-angle proton elastic scattering off the nuclei $^{12,14-17}$C have been measured in inverse kinematics at energies near 700 MeV/u at GSI Darmstadt. The hydrogen-filled ionization chamber IKAR served simultaneously as a gas target and a detector for the recoil protons. The projectile scattering angles were measured with multi-wire tracking detectors. The radial nuclear matter density distributions and the root-mean-square nuclear matter radii were deduced from the measured cross sections using the Glauber multiple-scattering theory. A possible neutron halo structure in $^{15}$C, $^{16}$C and $^{17}$C is discussed. The obtained data show evidence for a halo structure in the $^{15}$C nucleus.

The kinematics of multi-nucleon transfer reactions in 48Ca + 248Cm collisions at 262 MeV (center of target) was investigated by using a stacked-foil technique and radiochemical separations of trans-curium elements. Trans-curium isotopes were identified by α-particle spectroscopy. For Fm isotopes, by comparing the centroids of the measured post-neutron emission isotope distributions with the most probable primary mass number predicted by Volkov's generalized Q g g systematics, the missing mass (number of evaporated neutrons) is estimated. The latter is compared with that deduced from the measured centroid of the laboratory angular distribution peaked closely to the grazing angle and the centroid of the range distribution, being used to determine the average total kinetic energy loss (TKEL) and the average excitation energy. The latter agrees within the uncertainties with the missing mass so that a consistent picture of the reaction mechanism emerges. For products closer to the target Z, e.g., Cf and Bk, the distributions of kinetic energies are much broader than for Fm, reflecting the fact that in the former, values of TKEL reach from quasi-elastic scattering all the way to deep inelastic scattering. The measured laboratory angular distribution and the average laboratory kinetic energy of the Fm isotopes, being the prototypes for multi-nucleon transfer products, are benchmark values for the design of electromagnetic separators to be constructed for the separation and detection of unknown neutron-rich transactinides produced in this nuclear reaction type.

The search for He 4 - η bound states was performed with the WASA-at-COSY facility via the measurement of the excitation function for the d d → He 3 n π 0 and d d → He 3 p π − processes. The deuteron beam momentum was varied continuously between 2.127 GeV/c and 2.422 GeV/c, corresponding to the excess energy for the d d → He 4 η reaction ranging from Q = − 70 MeV to Q = 30 MeV . The luminosity was determined based on the d d → He 3 n reaction and the quasi-free proton–proton scattering via d d → p p n s p e c t a t o r n s p e c t a t o r reactions. The excitation functions, determined independently for the measured reactions, do not reveal a structure which could be interpreted as a narrow mesic nucleus. Therefore, the upper limits of the total cross sections for the bound state production and decay in d d → ( He 4 - η ) b o u n d → He 3 n π 0 and d d → ( He 4 - η ) b o u n d → He 3 p π − processes were determined taking into account the isospin relation between the both of the considered channels. The results of the analysis depend on the assumptions of the N ⁎ (1535) momentum distribution in the anticipated mesic- He 4 . Assuming, as in the previous works, that this is identical with the distribution of nucleons bound with 20 MeV in He 4 , we determined that (for the mesic bound state width in the range from 5 MeV to 50 MeV) the upper limits at 90% confidence level are about 3 nb and about 6 nb for n π 0 and p π − channels, respectively. However, based on the recent theoretical findings of the N ⁎ (1535) momentum distribution in the N ⁎ - He 3 nucleus bound by 3.6 MeV, we find that the WASA-at-COSY detector acceptance decreases and hence the corresponding upper limits are 5 nb and 10 nb for n π 0 and p π − channels respectively.

We investigate spectrum of bound and resonance states in 10Be, and scattering of alpha-particles on 6He. For this aim we make use of a three-cluster microscopic model. This model incorporates Gaussian and oscillator basis functions and reduces three-cluster Schrodinger equation to a two-body like many-channel problem with the two-cluster subsystem being in a bound or a pseudo-bound state. Much attention is given to the effects of cluster polarization on spectrum of bound and resonance states in 10Be, and on elastic and inelastic He6+α scattering.

Angular distributions of the elastic and inelastic scattering of 15N ions by 7Li nuclei were measured at the energy E lab ( N 15 ) = 81 MeV ( E c.m. = 25.77 MeV ) . The data were analyzed within the coupled-reaction-channels method. The elastic and inelastic scattering, spin reorientations of 7Li as well as the more important one- and two-step transfer reactions were included in the channels-coupling scheme. The parameters of Li 7 + N 15 optical potential of Woods–Saxon form as well as deformation parameters of these nuclei were deduced. The analysis showed that the forward angle elastic scattering is dominated by pure potential scattering whereas the middle and large angle scattering gets a contribution from the ground state reorientation of 7Li. Contributions from particle transfers were negligible for the present scattering system. The Li 7 + N 15 elastic scattering was compared with that of Li 7 + N 14 at the energies E lab ( N 14 ) = 80 MeV and 110 MeV. Different contributions to the elastic scatterings from other nuclear processes are shown to be responsible for the isotopic difference observed in the large angle scattering.

We calculate the coherent and incoherent production of J / ψ in PbPb ultraperipheral collisions (UPCs). The rapidity distributions of J / ψ in UPCs is the product of the photon flux distribution and the photon–nucleus cross section. The equivalent photon flux is computed in light-cone perturbation theory. The photon–nucleus cross section is calculated in the dipole model. We assume that two-gluon exchange contribution is coherent photonproduction cross section and the large- N c contribution provides an additional contribution to incoherent photonproduction cross section in photon–nucleus scattering. Our numerical results for the rapidity distributions of J / ψ production in PbPb UPCs at s N N = 2.76 TeV are compared to the experimental data measured by the ALICE Collaboration.

Heavy-flavor quarks are dominantly produced in initial hard scattering processes and experience the whole evolution of the system in heavy-ion collisions at RHIC energies. Thus they are suggested to be an excellent probe to the medium properties through their interaction with the medium. In this proceedings, we report our first measurement of D 0 production via topological reconstruction using STAR's recently installed Heavy Flavor Tracker (HFT). We also report our new measurement of Nuclear Modification Factor ( R A A ) of D 0 mesons in central Au+Au collisions at s N N = 200 GeV as a function of transverse momentum ( p T ). New results confirm the strong suppression at high p T with a much improved precision, and show that the R A A at high p T are comparable with light hadrons (π) and with D meson measurements at the LHC. Furthermore, several theoretical calculations are compared to our data, and with charm diffusion coefficient 2 π T D S ∼ 2 - 12 can reproduce both the D 0 R A A and v2 data in Au+Au collisions at RHIC.

The nuclear parton distribution function and flavor composition of hard scattering processes can be accurately studied using the jet fragmentation functions. Recent measurements of the pPb nuclear modification factor ( R pPb ), with diverging values for inclusive jets and charged hadrons, have raised question on jet fragmentation properties in pPb collisions. These spectra measurements are performed with pp reference at 5.02 TeV constructed by interpolation or extrapolation from different s , and on steeply falling power-law spectra. As the jet fragmentation function is only evolving logarithmically with s , this further underscores the importance of a direct measurement. Together with the CMS results in pPb inclusive jets and charged hadron R pPb , we introduce the new CMS measurement of fragmentation function in pPb collisions, where within our uncertainties, jets in pPb is found to have identical fragmentation property vs. pp jets. We will further discuss the consistency and tension among the results, and their possible origins. This measurement also gives important reference for the interpretation of the fragmentation function in PbPb collisions.

Since soft photons are unmodified once produced in heavy ion collisions, they give information about the entire thermal evolution of the medium. Excess photon yield over the expectation from initial hard scattering has been measured by PHENIX. In addition, PHENIX has measured a large azimuthal anisotropy, v2, of these soft photons with respect to the reaction plane. The large yield and v2 have been difficult to describe quantitatively and raise important questions about the early time dynamics in the medium. It is thus important to make more differential measurements to distinguish various potential explanations for this thermal photon puzzle. In this proceedings, we present yields, v2, and v3 of direct photons from s N N = 200 GeV A u + A u collisions.

The ALICE experiment has measured the direct photon spectra in Pb-Pb collisions at s N N = 2.76 TeV for three different centrality selections. The measurement was performed emplying a method utilizing conversion of photons into e + e − pairs in the detector material, and a method using the PHOS calorimeter. The two measurements were combined in order to measure direct photons over a broad transverse momentum range of 0.9 p T 14 GeV / c . A direct photon signal was observed in the thermal region 0.9 p T 2.1 GeV / c , with a significance of 2.6σ in the 20% most central collisions. The corresponding direct photon spectrum can be described by an exponential with an inverse slope parameter of ( 304 ± 11 s t a t ± 40 s y s t ) MeV, without subtracting the hard scattering component, which is somewhat larger than the inverse slope parameter of the direct photon spectrum at RHIC energies. Within uncertainties, the data can be described by different models for photon production in heavy-ion collisions. These proceedings provide a summary of the results published in [J. Adam, others (ALICE Collaboration), Direct photon production in Pb-Pb collisions at s N N = 2.76 TeV , arXiv:1509.07324 ] and [J. Adam, others (ALICE Collaboration), Supplemental figures: Direct photon production in Pb-Pb collisions at s N N = 2.76 TeV . URL https://cds.cern.ch/record/2102398 ].

The proton radiative capture 12,13C ( p , γ ) reactions at astrophysical energies, key processes in the CNO cycle, are revisited in the potential model with the proton-nucleus potential for both the scattering and bound states obtained in the folding model, using a realistic density dependent nucleon-nucleon interaction. For the consistency, this same folding model is also used to calculate the optical potential of the elastic p + 12 , 13 C scattering at energies around the Coulomb barrier. The folded p + 12 , 13 C optical potentials are shown to account well for both the elastic p + 12 , 13 C scattering and astrophysical S factors of the radiative capture 12,13C ( p , γ ) reactions.

The measurement of heavy-flavour production is a powerful tool to study the medium formed in high-energy heavy-ion collisions. Produced in hard scattering processes on a timescale shorter than the formation time of the Quark Gluon Plasma (QGP), they experience the whole evolution of the medium interacting with its constituents. The measurement of charm-hadron production allows testing the mechanisms of in-medium parton energy loss. Moreover, the study of charm-baryon production in heavy-ion collisions, and in particular the baryon-to-meson ratio, provides unique information on hadronisation mechanisms, constraining the role of coalescence. In this contribution, the ALICE results on open charmed meson and baryon production in large and small systems will be presented with a focus on the recent measurements of Λ c + / D 0 and D s + / D 0 ratios in central and peripheral Pb–Pb collisions and on the new results obtained for the same ratios in proton-proton collisions as a function of the charged particle multiplicity. The prospects for the Ξ c 0 analysis will also be discussed.

We calculate the radiative parton energy loss in the deeply inelastic scattering (DIS) off a large nucleus within a generalized high-twist approach. The final gluon radiation spectrum is a convolution of the hard partonic part and the transverse momentum dependent (TMD) quark-gluon correlation function, without the twist expansion in the transverse momentum of the initial gluons used in original high twist approach. The TMD quark-gluon correlation function can be factorized approximately as the product of initial quark distribution and TMD gluon distribution which can be used to define the generalized or TMD jet transport coefficient. The radiation spectrum will recover the Gylassy-Levai-Vitev (GLV) result in the first order of the opacity expansion, under the static scattering center and soft gluon radiation approximation. We also investigate numerically the difference as a result of the soft gluon radiation approximation, under the static scattering center approximation.

Cross sections for photon production in hadronic scattering processes have been calculated according to an effective chiral field theory. For $\pi + \rho \to \pi + \gamma$ and $\pi + \pi \to \rho + \gamma$ processes, these cross sections have been implemented into a novel hadronic transport approach (SMASH), which is suitable for collisions at low and intermediate energies. The implementation is verified by systematically comparing the thermal photon rate to theoretical expectations. The photon rates we obtain are compared to previous works, where scattering processes mediated by $\omega$ mesons are found to contribute significantly to the total photon production. Finally, the impact of considering the finite width of the $\rho$ meson is investigated, and a significant enhancement of photon production in the low-energy region is observed. This work is the first step towards a consistent treatment of photon emission in hybrid hydrodynamics+transport approaches. The quantification of the importance of the hadronic stage for the resolution of the direct photon flow puzzle is a next step and can be applied to identify equilibrium and non-equilibrium effects in the hadronic afterburner., Comment: 4 pages, 3 figures, proceedings of Quark Matter 2019

Bottomonia are produced by hard scattering in the early times of a relativistic heavy-ion collision, so they serve as excellent probes of the quark-gluon plasma (QGP). Early CMS data showed that the yields of the ϒ(1S), ϒ(2S), and ϒ(3S) mesons are suppressed in PbPb relative to those in pp. In order to interpret the results in PbPb collision unambiguously, the cold nuclear matter effects need to be quantitatively estimated using pPb collisions data. Additionally, the measurement of the elliptic azimuthal anisotropy of bottomonium states have been suggested as a powerful tool to study the different in-medium effects such as dissociation and regeneration. In these proceedings, the new bottomonium results are reported for pPb and PbPb collisions data at 5.02 TeV with the CMS detector. First, the nuclear modification factors of the ϒ(1S), ϒ(2S), and ϒ(3S) mesons are presented in pPb collisions as functions of the transverse momentum and rapidity. Then, the new measurements of the azimuthal anisotropy (ν2) of the ϒ(1S) and ϒ(2S) mesons are reported using PbPb collisions data at 5.02 TeV taken in 2018.

Recently a new $\Delta$ method for deducing the energy and asymptotic normalization coefficient (ANC) from phase-shift data has been formulated and applied to resonance states. This differs from the conventional effective-range function (ERF) method by fitting only the nuclear part of the ERF. It also differs from the method which was proposed for bound states by Ram\'irez Su\'arez and Sparenberg (see Ref. below) which also named the $\Delta$ method where a pole condition defines by the Eq. $\Delta_l=0$ ($\Delta_l$ is the function in the ERF determined only by the scattering phase shift). Here the standard pole condition, including the Coulomb part into the relate equation, is used for a resonant state. It has been shown that the ERF method does not work for large-charge colliding nuclei. Moreover, even for lower charges it is not clear that the results of the ERF method are accurately enough. The Coulomb part forms a background, which smooths an ERF energy dependence. Therefore, one needs to find when the ERF method becomes inaccurate and this requires recalculating some published results by the $\Delta$ method. This project has already been started in a recent paper for resonances in the $\alpha$-$\alpha$ scattering. Here this method is applied using the $\Delta_l$-function fittings to the experimental $p$-${}^4$He scattering phase-shift data in the $P_{3/2}$ and $P_{1/2}$ resonance states. The calculation results are compared with those obtained earlier by the ERF method. The main changes concern resonance energy and width., Comment: 7 pages, 1 figure, 1 table. This preprint differs from arXiv:2004.12855 by corrections of typos and adding 2 equations

Electron scattering is an effective method to study the nuclear structure. For the odd- A nuclei with proton holes in the outmost orbits, we investigate the contributions of proton holes to the nuclear quadrupole moments Q and magnetic moments μ by the multiple Coulomb scattering and magnetic scattering. The deformed nuclear charge densities are constructed by the relativistic mean-field (RMF) models. Comparing the theoretical Coulomb and magnetic form factors with the experimental data, the nuclear quadrupole moments Q and nuclear magnetic moments μ are investigated. From the electron scattering, the wave functions of the proton holes of odd- A nuclei can be tested, which can also reflect the validity of the nuclear structure model.

Angular distributions of the 9 Be + 15 N elastic and inelastic scattering were measured at E lab ( 15 N) = 84 MeV ( E c.m. = 31.5 MeV) for the 0–6.76 MeV states of 9 Be and 0–6.32 MeV states of 15 N. The data were analyzed within the optical model and coupled-reaction-channels method. The elastic and inelastic scattering, spin reorientations of 9 Be in ground and excited states and 15 N in excited states as well as the most important one- and two-step transfer reactions were included in the channels-coupling scheme. The parameters of the 9 Be + 15 N optical potential of Woods–Saxon form as well as deformation parameters of these nuclei were deduced. The analysis showed that the 9 Be + 15 N pure potential elastic scattering dominates at the forward angles whereas the ground state spin reorientation of 9 Be gives a major contribution to the elastic scattering cross sections at the large angles. Contributions from particle transfers are found to be negligible for the present scattering system.

Deuteron–nucleus scattering is described using exact three-particle equations. The theory is formulated in an extended Hilbert space allowing the excitation of the target nucleus. Alt, Grassberger, and Sandhas equations for transition operators are solved in the momentum-space framework including the Coulomb interaction via the screening and renormalization method. The calculations are performed for elastic and inelastic scattering of deuterons on 24Mg using the rotational model for the excitation potential. A reasonable agreement with the experimental data for the first excited state 2 + of 24Mg is achieved when the quadrupole deformation parameter β 2 = 0.47 is used. This new value is more consistent with the inelastic proton scattering data requiring β 2 ≈ 0.5 than previous determinations β 2 ≈ 0.4 based on two-body deuteron–nucleus models.

Two sets of data for dα scattering are analysed to determine the parameters of the bound and resonant states of the nuclear system Li 6 with quantum numbers 1 + , 2 + , 3 + , 2 − , and 3 − , as well as to find the corresponding S-matrix residues. These data (dα cross-sections) are fitted by both a single-channel and a two-channel S-matrix that is written in terms of semi-analytic Jost matrices, where all the factors, responsible for the branching of the energy Riemann surface, are given explicitly and exactly while the remaining unknown functions are represented by power series with the coefficients being the fitting parameters. The Jost matrices obtained from the fitting, are used at complex energies to locate resonances and the bound state, as well as to determine the corresponding S-matrix residues and the Asymptotic Normalization Coefficients (ANC). Our analysis, based on an S-matrix with the correct analytic structure, gives a solid confirmation of the resonance parameters found by the other authors.

We examined several low- Q 2 elastic ep and ed scattering data sets using various models to extract the proton and deuteron rms radii and developed a comprehensive algorithm for estimating the systematic bias of each extracted radius. In each case, we chose the model and upper bound for Q 2 that minimized the combination of statistical uncertainty and bias. We attribute the discrepancy between small (≈0.84 fm) and large (≈0.88 fm) proton radius extractions to the absence of data that can accurately isolate the linear and quadratic contributions to the form factor at low- Q 2 . In light of this ambiguity, we estimated the model-dependence of each extracted radius by studying the distribution of many possible fits. The resulting radii are 0.842(4) fm for the proton and 2.092(19) fm for the deuteron. These results indicate radii consistent with those determined from muonic hydrogen and deuterium measurements.

The S-wave ΛΛ and NΞ interactions are studied on the basis of the (2+1)-flavor lattice QCD simulations close to the physical point ( m π ≃ 146 MeV and m K ≃ 525 MeV ). Lattice QCD potentials in four different spin-isospin channels are extracted by using the coupled-channel HAL QCD method and are parametrized by analytic functions to calculate the scattering phase shifts. The ΛΛ interaction at low energies shows only a weak attraction, which does not provide a bound or resonant dihyperon. The NΞ interaction in the spin-singlet and isospin-singlet channel is most attractive and lead the NΞ system near unitarity. Relevance to the strangeness = −2 hypernuclei as well as to two-baryon correlations in proton-proton, proton-nucleus and nucleus-nucleus collisions is also discussed.

We predict glueball/oddball resonances lying on the pomeron/odderon trajectories. A simple new form of the trajectories, with threshold and asymptotic behaviour required by analyticity and unitarity, is proposed. The parameters of these (pomeron and odderon) trajectories are fitted to the data on high-energy elastic proton-proton scattering. The fitted trajectories are extrapolated to the resonance region to predict masses and widths of glueballs and oddballs. The (pomeron and odderon) trajectories may be used to calculate processes of central exclusive diffraction (CED)., Comment: 37 pages, 15 figures, 5 tables

To describe the elastic scattering cross sections of C 12 − 12 C and O 16 − 16 O systems, in our recent work (RM1), the double-folding (DF) model potentials was calculated via the density-dependent averaged effective two-body nucleon-nucleon (NN) interaction (DDAEI). The DDAEI can be generated through the lowest order constrained variational (LOCV) method for the symmetric nuclear matter (SNM), with the input bare Reid68 NN potential. Then the DF potentials were directly inserted into the FRESCO code to find the differential cross-sections (DCS). The result was encouraging with respect to the experimental data and the other theoretical works. In the present report, the above folded potentials are fitted through a Woods-Saxon (WS) shell model potential, which can easily be used (through the WS parameters) as an input to the FRESCO code, without any approximation. The calculated DCS are compared with the corresponding calculations coming from the fitting procedures with the input finite range DDM3Y1-Reid68 potential, RM1 and the available experimental data at different incident energies. As in RM1, it is shown that a reasonable description of scattering data at the low and the medium energies for the elastic scattering of the C 12 − 12 C and O 16 − 16 O systems can be obtained in the framework of the above LOCV-DDAEI, without any need for defining a parameterized density dependent function in the effective NN potential, which is formally considered in the typical DDM3Y1-Reid68 interactions. The χ 2 fits are calculated and discussed. Our result based on DF WS potential parameters, i.e., WS-FRESCO DCS, are approximately in agreement to those of RM1. Finally, the generated energy dependent WS potentials can be directly used in the future calculations and considered as an approximate energy dependent shell model one-body potential which is based on the phenomenological NN interaction.

The description of particles with spin in high energy reaction can be attained by using a spin density matrix. In this paper we introduce the spin density matrix for spin-3/2 particles. With this matrix, we present the complete twist-4 results for the e + e − → Ω X at the tree level of perturbative quantum chromodynamics. The calculations are carried out by applying the collinear expansion. In the collinear expansion formalism the multiple gluon scattering is taken into account and gauge links are obtained systematically and automatically. We present the complete results for structure functions and the polarizations of the produced hadron in terms of gauge invariant fragmentation functions up to twist-4. We obtain 28 structure functions, among them 8 are leading twist, 12 are twist-3, 4 are twist-4 and the others do not correspond to fragmentation functions. We also obtain 3 longitudinal and 6 transverse polarizations. For the complete twist-4 calculation, the four-quark correlator contributions are also considered in this paper.

The lowest order constrained variational (LOCV) formalism is formulated for the Nijmegen soft-core potential, which is fitted by the proton-proton (pp) scattering phase shift. The calculations are performed for the equation of state (EOS) of both nuclear and neutron matter. The state-dependent correlation functions are calculated by the minimization of two-body cluster energy, and the resulting Euler Lagrange equations are solved for this kind of potential. It is shown that LOCV calculations can work with this kind of interaction as well as other interactions in configuration space. The state-dependent correlation functions are calculated by minimization of two-body cluster energy for each channel with various J L S T M T , by using Nijmegen interaction. The correlation functions are compared with those coming from UV14 interaction in LOCV formalism. It is shown that unlike UV14, AV14, and AV18 potentials, the binding energy obtained from Nijmegen in the LOCV framework is −16.81 MeV that is close to the experimental value. Finally, it is recognized our LOCV results with Nijmegen interaction are similar to calculations with different interactions and different many-body methods.

Precision phenomenology at the LHC requires the inclusion of higher order QED corrections effects to the processes of proton-proton scattering. In this work, we show how the parton distribution functions (PDFs) could be analytically determined, which is currently accurate up to NLO in QCD and NLO in QED, including the relevant mixed QCD plus QED corrections. We depict our results for evolved PDFs, using the inputs from the xFitter framework, and compare them with the results of the other PDFs sets as well as the running results from the APFEL program at the concerned approximation. We also obtain the proton structure function, including the heavy quark structure functions based on the Mellin transform techniques. We show how our outgoing results yield a proper representation for F 2 p ( x , Q 2 ) , F 2 c ( x , Q 2 ) and F 2 b ( x , Q 2 ) in terms of the PDFs. We compare the structure functions with the experimental data and the running APFEL program results which indicate a good agreement with each other.

The possibility of describing the available experimental data for the total cross section for the reaction of the neutron capture on 10B at energies from 25.3 meV to 1.0 MeV was considered in the framework of the modified potential cluster model with forbidden states, with the classification of the orbital cluster states according to Young diagrams and taking into account the resonance behavior of phase shifts of the n 10 B elastic scattering. The obtained results are found to be in agreement with the experimental measurements. The calculated total cross sections are used for obtaining the reaction rate of the neutron capture on 10B at the temperature range of 0.01 to 10 T 9 . The reaction rate increases essentially at temperatures above 0.3–0.4 T 9 , conditioned by the resonances at energy above 100 keV. The results obtained here demonstrate the validity of the used model to this reaction, without taking into account coupling of channels or the imaginary component of potential.