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arXiv2009

Physics Program with Tagged Forward Protons at STAR/RHIC

A new effort to explore the diffractive regime in polarized $p+p$ collisions in a broad high energy range ($\sqrt{s}$ = 200 - 500 GeV) has been initiated with the STAR detector at RHIC. Staged implementation of multiple Roman Pot stations for tagging the forward proton in the diffractive processes will enable searches for the centrally produced for the possible gluon bound state via double Pomeron exchange process and the theoretically expected Odderon state in QCD by studying spin-dependent elastic scattering in a wide $t$-range with polarized $p+p$.

hep-ex↗
arXiv2009

Yields and elliptic flow of $d(\bar{d})$ and $^{3}He(\bar{^{3}He})$ in Au+Au collisions at $\sqrt{s_{_{NN}}} =$ 200 GeV

We present the $p_{T}$ spectra, elliptic flow ($v_2$) and coalescence parameters $B_{2}$ for $d$, $\bar{d}$ ($1<p_{T}<4$ GeV/c) and $B_{3}$ for $^{3}He$, $\bar{^{3}He}$ ($2<p_{T}<6$ GeV/c) produced at mid-rapidity in Au+Au col lisions at $\sqrt{s_{_{NN}}} = 200$ GeV. The results are measured in the STAR experiment at RHIC. The spectra of the light nuclei show softer $p_T$ distributions than calculations from a blast-wave model in which the parameters were fixed from pion, kaon and proton $v_2$($p_T$) and $p_T$ distributions. The coalescence volume is found to track with pion HBT re sults for different collision geometries. The $v_2$ measurement for $d(\overline{d})$ as a function of transverse momentum $p_T$ is found to follow an approximate atomic mass number ($A$) scaling while that of $^{3}He(\bar{^{3}He}) $ deviates slightly from the scaling. A negative $v_{2}$ has been observed for $\bar{d}$ at low $p_{T}$, consiste nt with large radial flow in Au+Au collisions.

nucl-ex↗
arXiv2009

The QCD Phase Diagram: Expectations and Challenges

A survey is given of recent QCD theory advances concerning the phase diagram, in particular the indications for a critical point and adjacent first order phase transition at high baryo-chemical potential, and the new ideas concerning a further phase at high $μ_{B}$, the quarkyonic matter phase. The latter state might finally explain the hadro-chemical equilibrium freeze-out points from A+A collisions at energies below SPS energy. We review several event-by-event fluctuation signals that promise to shed a light on the existence of a critical point, and we discuss its possible reflection in recent lattice QCD calculations.

nucl-ex↗
arXiv2010

Discrimination between roles of fissioning nucleus and asymmetry degree of freedom on the even-odd structure in fission-fragment yields

Based on a wide systematics of fission-fragment distributions measured in low-energy fission, the even-odd staggering in the fission-fragment element yields is investigated. The well-established evolution of the global even-odd effect with the fissioning system is found to be only a partial aspect of the even-odd structure. Indeed, it is shown that the global even-odd effect is varying systematically with the mean asymmetry of the fission-fragment distribution, and that the general increase of the even-odd staggering with asymmetry is depending on the fissioning system. Thus, the dependency of the even-odd effect with the fissioning system is accredited in part to the asymmetry evolution of the charge distribution, and not solely related to the dissipated energy as it has been done earlier. This interpretation is strongly supported by data measured in inverse kinematics, which cover the complete charge distribution and include precise yields at symmetry. The relevance of the order parameter to describe the even-odd effect in fission-fragment yields as a general property is explored.

nucl-ex↗
arXiv2010

Determination of the total width of the eta-prime meson

The aim of this work was to determine the total width of the eta-prime meson. The investigated meson was produced via the pp->ppeta-prime reaction in the collisions of beam protons from COSY synchrotron with protons from a hydrogen cluster target. The COSY-11 detector was used for the measurement of the four-momentum vectors of outgoing protons. The mass of unregistered meson was determined via the missing mass technique, while the total width was directly derived from the mass distributions established at five different beam momenta. Parallel monitoring of the crucial parameters (e.g. size and position of the target stream) and the measurement close-to-threshold permitted to obtain mass resolution of FWHM = 0.33 MeV/c^2. Based on the sample of more than 2300 reconstructed pp->ppeta-prime events the determined total width of the eta-prime meson amounts to 0.226+-0.017(stat.)+-0.014(syst.) MeV, which is the most precise measurement until now.

nucl-ex↗
arXiv2009

Dispersion sum rules for pion polarizabilities

An analysis of different dispersion sum rules (DSRs) for the dipole and quadrupole pion polarizabilities is carried out. We prove the absence of additional spurious singularities in these approaches. The results of the calculations of the polarizabilities in the framework of DSRs are compared with ChPT predictions and with data obtained in different experiments.

hep-ph↗
arXiv2009

Particle Production in Au+Au Collisions at $\sqrt{s_{NN}}$ = 9.2 GeV

In this report we present the first test run results from Au+Au collisions at $\sqrt{s_{NN}}$ = 9.2 GeV at RHIC. The large acceptance STAR detector has collected ~3k minimum bias collisions during this test run. The azimuthal anisotropy, identified particle spectra, particle ratios and HBT radii are observed to be consistent with the previous measurements from CERN SPS at similar center of mass energies. These results from the lowest collision energy at RHIC demonstrate the STAR detector's readiness to collect high quality data for the proposed Critical Point Search Program which allows us to explore the QCD phase diagram.

nucl-ex↗
arXiv2009

New experiment on the neutron radiative decay

The report is dedicated to the preparation of the new experiment on the neutron radiative decay what is conducted for the last years. We started the experimental research of this neutron decay branch with the experiment conducted at ILL in 2002 and continued in another experiment at the second and third cycles at the FRMII reactor of the Technical University of Munich in 2005. In the first experiment we succeeded in measuring only the upper limit on the relative intensity (B.R.) of the radiative neutron decay and in the second we succeeded in discovering events of radiative neutron decay and measure its B.R.=(3.2+-1.6)10-3 (with C.L.=99.7% and gamma quanta energy over 35 keV). The obtained average B.R. value was approximately twice the theoretical value calculated earlier within the framework of the standard electroweak model. However, due to significant experimental error it would be preliminary to deduce that based on this finding a deviation from the standard model has been observed. To prove or disprove the existence of a deviation it is necessary to conduct a new experiment that would allow to measure the radiative peak in timing spectra with precision in the order of 1%. By the present time we have prepared a new experiment the main result of which would be the measurement of B.R. for the radiative branch of neutron decay with this precision.

nucl-ex↗
arXiv2009

Single-nucleon experiments

We discuss the Jefferson Lab low momentum transfer data on moments of the nucleon spin structure functions $g_1$ and $g_2$ and on single charged pion electroproduction off polarized proton and polarized neutron. A wealth of data is now available, while more is being analyzed or expected to be taken in the upcoming years. Given the low momentum transfer selected by the experiments, these data can be compared to calculations from Chiral Perturbation theory, the effective theory of strong force that should describe it at low momentum transfer. The data on various moments and the respective calculations do not consistently agree. In particular, experimental data for higher moments disagree with the calculations.The absence of contribution from the $Δ$ resonance in the various observables was expected to facilitate the calculations and hence make the theory predictions either more robust or valid over a larger $Q^2$ range. Such expectation is verified only for the Bjorken sum, but not for other observables in which the $Δ$ is suppressed. Preliminary results on pion electroproduction off polarized nucleons are also presented and compared to phenomenological models for which contributions from different resonances are varied. Chiral Perturbation calculations of these observables, while not yet available, would be valuable and, together with these data, would provide an extensive test of the effective theory.

nucl-ex↗
arXiv2009

Nucleon form factors with Nf=2 dynamical twisted mass fermions

We present results on the electromagnetic and axial nucleon form factors using two degenerate flavors of twisted mass fermions on lattices of spatial size 2.1 fm and 2.7 fm and a lattice spacing of about 0.09 fm. We consider pion masses in the range of 260-470 MeV. We chirally extrapolate results on the nucleon axial ch arge, the isovector Dirac and Pauli root mean squared radii and magnetic moment to the physical point and co mpare to experiment.

hep-lat↗
arXiv2009

Delta electromagnetic form factors and quark transverse charge densities from lattice QCD

We discuss the techniques to extract the electromagnetic Delta form factors in Lattice QCD. We evaluate these form factors using dynamical fermions with smallest pion mass of about 350 MeV. We pay particular attention to the extraction of the electric quadrupole form factor that signals a deformation of the Delta. The magnetic moment of the $Δ$ is extrapolated using a chiral effective field theory. Using the form factors we evaluate the transverse density distributions in the infinite momentum frame showing deformation in the Delta.

hep-lat↗
arXiv2009

Fluctuations in relativistic heavy-ion collisions from the Glauber models

In the first part of the talk we discuss the role of the two-body nucleon-nucleon correlations on signatures of the heavy-ion collisions which are a priori expected to be sensitive to these effects. We find that while the fluctuations of the number of produced particles are indeed affected, other quantities (v_2 fluctuations, size fluctuations) are insensitive to the presence of the NN correlations in the nucleon distributions. In the second part we show that the fluctuations of the transverse size of the initial source cause, after a suitable hydrodynamic evolution, fluctuations of the transverse flow velocity at hadronic freeze-out. This in turn yields the event-by-event fluctuations of the transverse momentum of the produced particles, p_T. Our results demonstrate that practically all of the observed event-by-event p_T fluctuations may be explained this way.

nucl-th↗
arXiv2009

Charmonium production at the LHC

We summarize the perspectives on quarkonium, in particular charmonium, detection at the LHC, both for proton-proton and heavy-ion collisions. We give a review of the experimental capabilities of the four LHC detectors: ALICE, ATLAS, CMS and LHCb.

nucl-ex↗
arXiv2010

NA49 and NA61/SHINE experiments: results and perspectives

The Super Proton Synchrotron (SPS) covers one of the most interesting regions of the QCD phase diagram $(T - μ_B)$. On the one hand there are indications that the energy threshold for deconfinement is reached already at low SPS energies. On the other hand theoretical calculations locate the QCD critical end-point at energies accessible at the SPS. In this paper the NA49 signatures of the onset of deconfinement are presented. Results are shown on pion production, the kaon to pion ratio, slopes of transverse mass spectra ("temperature"), and event-by-event particle ratio fluctuations versus collision energy, for central $Pb+Pb$ interactions. Next we show possible indications of the critical point in event-by-event mean transverse momentum and multiplicity fluctuations. Finally we discuss the future ion program of the NA61/SHINE experiment (energy scan with light ions).

nucl-ex↗
arXiv2009

Transversity Generalized Parton Distributions from gamma N -> pi rhot N' with a Large pi rhot Invariant Mass

The chiral-odd transversity generalized parton distributions of the nucleon can be accessed experimentally through the exclusive photoproduction process gamma N -> pi rhoT N', with or without beam and target polarization, provided the vector meson is produced in a transversely polarized state. The kinematical domain of factorization is defined through a large invariant mass of the meson pair and a small transverse momentum of the final nucleon. We calculate perturbatively the scattering amplitude at leading order in alpha_s and build a simple model for the dominant transversity GPD H_T(x, xi, t) based on the concept of double distribution. Counting rate estimates are in progress.

hep-ph↗
arXiv2010

Discovery of the Mercury Isotopes

Forty mercury isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

nucl-ex↗