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Few-Nucleon Systems: Notes about the Status and Results of Investigations

Radiation technologies have found wide application in power engineering, medicine, biology and other areas of human activities. However, theoretical calculations of nuclear reactions and, correspondingly, the interpretation of experimental results appear model-dependent. The model-independent calculation of the nuclear reaction must take into account the structure of the nuclear ground state, the final-state nucleon interaction and the contribution of meson exchange currents. These calculations can be carried out only with due regard for realistic NN and 3N forces between nucleons and also, with the use of exact methods of solving the many-body problem. In this technique it is expedient to conduct investigations of nuclear reactions as from few-nucleon systems in the energy area of the particles below the meson-producing threshold. The tensor part of NN interaction and 3NF,s generate the lightest nuclei states with nonzero orbital momenta of nucleons. These states in the lightest nuclei is conditioned the properties of inter-nucleonic forces, and therefore, similar effects should be observed unexceptionally in all nuclei. The review papers are generally devoted to three-nucleon systems. In this paper primary attention is given to the investigation of the $^4$He nucleus.

nucl-ex↗

Neutron-4He Resonant Scattering at d-3H Threshold

Speed plot and time delay analysis confirms a two-pole S-matrix structure of the lowest 3/2+ level in 5He. Real parts of neutron-alpha elastic and 4He(n,d)3H reaction pole energies are 17.669+/-0.006 and 17.705+/-0.001 MeV n-4He c.m., respectively. Neutron-alpha elastic resonance, uncorrected for experimental energy spread, is characterized by deuteron and neutron partial widths ca. 0.008 and 0.030 MeV suggested by previous time delay analysis.

nucl-th↗

Study of $^{124}$Sn+$^{136}$Xe fusion-evaporation: analysis of a rare-event experiment

Fusion-evaporation in the $^{124}$Sn+$^{136}$Xe system is studied using a high intensity xenon beam provided by the Ganil accelerator and the LISE3 wien filter for the selection of the products. Due to the mass symmetry of the entrance system, the rejection of the beam by the spectrometer was of the order of $5times10^8$. We have thus performed a detailed statistical analysis to estimate random events and to infer the fusion-evaporation cross sections. No signicant decay events were detected and upper limit cross sections of 172 pb, 87 pb and 235 pb were deduced for the synthesis of $^{257}$Rf, $^{258}$Rf and $^{259}$Rf, respectively.

nucl-ex↗

Description of the Totem experimental data on elastic pp-scattering at sqrt(s)=7 TeV in the framework of unified systematic of elastic scattering data

An unified systematic of elastic (anti)proton-proton scattering data is proposed based on a simple expression for the process amplitude - f(q)=A[(πdq)/sh(πdq)][i J_1(Rq)/(Rq)+ρJ_0(Rq)]. The parameters R and d are obtained at a fitting of (anti)proton-proton experimental data on differential cross sections from Plab=1 GeV/c up to ISR energies. The fitting gives extra-ordinary good results, χ^2/NoF ~ 1 of below at |t|< 1.75 (GeV/c)^2. An extrapolation of the parameter's energy dependencies to the LHC energies allows excellent description of the Totem data up to the second diffraction maximum. Predictions for other LHC energies are presented also. The amplitude provides one with parameterizations of total and elastic cross sections. Its impact parameter representation corresponds to the 2-dimensional Fermi-function - 1/[1+exp((b-R)/d)], which is very useful for Glauber calculations of nucleus-nucleus cross sections at super high energies. It is shown for the first time that experimental high |t| elastic scattering has a weak energy dependency. This allows to describe high |t| tail of the Totem data.

hep-ph↗

ALICE Overview

A general overview of the results obtained by the ALICE experiment from the analysis of the $\PbPb$ data sample collected at the end of 2010 during the first heavy-ion run at the LHC is presented.

nucl-ex↗

Results of a search for 2β-decay of Xe-136 with high pressure copper proportional counters in Baksan Neutrino Observatory INR RAS

Search for ββ-decay of Xe-136 with two high pressure proportional counters is carried out in Baksan Neutrino Observatory. The experiment is based on comparision of spectra measured with natural and enriched xenon. The measured halfe life is equal to T_{1/2}=5.5^{+4.6}_{-1.7} \cdot 10^{21} yr (67% C.L.) for ββ2ν-decay mode. No evidence has been found for neutrinoless ββ-decay. The decay half life limit based on data measured during 17280 h is T_{1/2}(ββ0ν)\geq 4.9 \cdot 10^{23} yr (90% C.L.).

nucl-ex↗

Nuclear modification of charged hadron production at LHC

We analyze the recent results for suppressed production of charged hadrons for Pb+Pb collisions at the center of mass energy of 2.76 TeV/nucleon-pair. We closely follow the treatment used recently by us where partons lose energy due to radiation of gluons following multiple scatterings while traversing the quark gluon plasma, before fragmenting into hadrons at the center of mass energy of 200 GeV/nucleon-pair. We obtain an empirical value for the momentum transport coefficient $(\widehat{q})$ and provide predictions for azimuthal anisotropy of hadron momenta for non-central collisions.

nucl-th↗

Experimental research of double beta decay of atomic nuclei

Results of several double beta decay experiments, performed with the help of low background crystal scintillators, are presented. In particular, the half-life value of the two-neutrino double beta decay of 116-Cd has been measured as 2.9 10^{19} yr, and the new half-life limit on the neutrinoless double beta decay of 116-Cd has been established as >1.7 10^{23} yr at 90%, which corresponds to a restriction on the neutrino mass <1.7 eV. New half-life bounds on the level of 10^{17}-10^{21} yr were set for double beta processes in 64-Zn, 70-Zn, 106-Cd, 108-Cd, 114-Cd, 136-Ce, 138-Ce, 142-Ce, 160-Gd, 180-W, and 186-W by using low-background CdWO4, GSO, and ZnWO4 crystal scintillators. The claim of discovery of the neutrinoless double beta decay of 76-Ge [Mod. Phys. Lett. A 16 (2001) 2409] was analyzed. The demands of the future high sensitivity double beta decay experiments, aiming to observe the neutrinoless double beta decay or to advance restrictions on the neutrino mass to < 0.01 eV, were considered. Requirements for their sensitivity and discovery potential were formulated. Two projects of double beta experiments with a sensitivity on the level of 10^{26}-10^{27} yr (CAMEO and CARVEL projects) were discussed. Scintillation properties and radioactive contamination of CaWO4, ZnWO4, CdWO4, PbWO4, GSO(Ce), CeF3, yttrium-aluminum garnet doped with neodymium (YAG:Nd) crystal scintillators were studied. Applicability of these scintillators to search for double beta decay was discussed.

nucl-ex↗

Measures of radioactivity: a tool for understanding statistical data analysis

A learning path on radioactivity in the last class of high school is presented. An introduction to radioactivity and nuclear phenomenology is followed by measurements of natural radioactivity. Background and weak sources are monitored for days or weeks. The data are analyzed in order to understand the importance of statistical analysis in modern physics.

physics.ed-ph↗

Highlights from Heavy Ion Collisions at RHIC and the Acoustics of the Little Bangs

At the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, heavy nuclei are collided at high energies to create matter that is hot enough and dense enough to dissolve hadrons into a quark-gluon-plasma (QGP). In this lecture, dedicated to the memory of Aditya Sambamurti, I present an introduction to heavy-ion collisions and highlights from the first decade of RHIC results.

nucl-ex↗

Charge Dependence and Scaling Properties of Dynamical $K/π$, $p/π$, and $K/p$ Fluctuations from the STAR Experiment

Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be enhanced near a QCD critical point. Charge dependent results from new measurements of dynamical $K/π$, $p/π$, and $K/p$ ratio fluctuations are presented. The STAR experiment has performed a comprehensive study of the energy dependence of these dynamical fluctuations in Au+Au collisions at the energies $\sqrt{s_{NN}}$ = 7.7-200 GeV using the observable, $ν_{\rm dyn}$. These results are compared to previous measurements and to theoretical predictions. Various proposed scaling scenarios that attempt to remove the intrinsic volume dependence of $ν_{\rm dyn}$ and to simplify comparisons between experimental measurements are also considered. Constructing an intensive quantity allows for a direct connection to thermodynamic predictions.

nucl-ex↗

Probing Strangeness in Hard Processes

Since the discovery of strangeness almost five decades ago, interest in this degree of freedom has grown up and now its investigation spans the scales from quarks to nuclei. Measurements with identified strange hadrons can provide important information on several hot topics in hadronic physics: the strange distribution and fragmentation functions, the nucleon tomography and quark orbital momentum, accessible through the study of the {\it generalized} parton distribution and the {\it transverse momentum dependent} parton distribution functions, the quark hadronization in the nuclear medium, the hadron spectroscopy and the search for exotic mesons. The CLAS12 large acceptance spectrometer in Hall B at the Jefferson Laboratory upgraded with a RICH detector together with the 12 GeV CEBAF high intensity, high polarized electron beam can open new possibilities to study strangeness in hard processes allowing breakthroughs in all those areas. This paper summarizes the physics case for a RICH detector for CLAS12. Many topics have been intensively discussed at the International Workshop "Probing Strangeness in Hard Processes" (PSHP2010) \cite{PSHP-workshop} held in Frascati, Italy in October 2010. The authors of this papers like to thank all speakers and participants of the workshop for their contribution and very fruitful discussion.

hep-ex↗

The GRANIT project: Status and Perspectives

The GRANIT project is the follow-up of the pioneering experiments that first observed the quantum states of neutrons trapped in the earth's gravitational field at the Institute Laue Langevin (ILL). Due to the weakness of the gravitational force, these quantum states exhibit most unusual properties: peV energies and spatial extensions of order 10 $μ$m. Whereas the first series of observations aimed at measuring the properties of the wave functions, the GRANIT experiment will induce resonant transitions between states thus accessing to spectroscopic measurements. After a brief reminder of achieved results, the principle and the status of the experiment, presently under commissioning at the ILL, will be given. In the second part, we will discuss the potential of GRANIT to search for new physics, in particular to a modified Newton law in the micrometer range.

nucl-ex↗

Testing new strongly intensive measures of transverse momentum fluctuations

Recently, the new strongly intensive measures of fluctuations $Δ$ and $Σ$ have been proposed. In this publication their properties are tested using an example of event-by-event transverse momentum fluctuations. The obtained values are compared to the long used $Φ$ measure of pT fluctuations. Several tests are preformed within data produced by fast generators, as well as by the UrQMD model. The UrQMD calculations are presented for the systems and energies which are planned to be studied in the NA61/SHINE experiment at the CERN Super Proton Synchrotron.

nucl-th↗

Effect of a $Λ$ impurity in doubly magic nuclei

We study the effect of a $Λ$ hyperon immersed in the doubly magic nuclei, $^{16}$O, $^{40}$Ca, $^{48}$Ca, and $^{208}$Pb, as well as the neutron magic nucleus $^{90}$Zr. For a $Λ$ in the $1s$ and $1p$ states in $^{17}_Λ$O, $^{41}_Λ$Ca, $^{49}_Λ$Ca, $^{91}_Λ$Zr, and $^{209}_Λ$Pb, we compare the single-particle energies and density distributions of the core nucleons with those of the nuclei without the $Λ$, as well as the point proton and neutron radii. A remarkable finding is that the bound $Λ$ induces a significant asymmetry in the proton-neutron density distributions in the core nucleus. This in turn gives rise to an appreciable, iso-vector mean field. As a consequence, the neutrons in the core are more attracted to the center of the nucleus, while the protons are pushed away, in comparison with those in the corresponding nucleus without the $Λ$.

nucl-th↗

Charge fluctuations in Pb--Pb collisions at $\sqrt{s_{NN}} = $2.76 TeV measured by ALICE experiment

Charge fluctuations provide a possible signature for the existence of the de-confined Quark Gluon Plasma phase (QGP). Being sensitive to the square of the charges, fluctuations in QGP, with fractionally charged partons, are significantly different from those of a hadron gas with unit charged particles. Studies of charge fluctuations have been carried out using the variable, $ν_{(+-,dyn)}$ which, by its construction, is free from collisional bias (impact parameter fluctuations and fluctuations from the finite number of charged particles within the detector acceptance). The dependence of charge fluctuations on the pseudo--rapidity windows for various centrality bins is analyzed for Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV in the ALICE experiment at CERN-LHC. A scaling behavior is observed as a function of increasing pseudo-rapidity window for the charge fluctuations, expressed in terms of \nchnudyn, where $N_{ch}$ is the number of charged particles. The results are compared to experimental measurements at lower energies and to model predictions.

nucl-ex↗

Empirical Fit to electron-nucleus scattering

An empirical fit to electron-nucleus scattering for $A>2$ is made based on world data. It is valid for $0<W<3.2$ GeV and $0.2<Q^2<5$ GeV$^2$, and can be used with caution at lower $Q^2$. The fit is based on previous empirical fits to electron-proton and electron-neutron scattering, taking into account the effects of Fermi motion plus a substantial extra contribution that fills in the dip between the quasi-elastic peak and the $Δ(1232)$ resonance.

nucl-th↗

Femtoscopy of proton-proton collisions at the LHC with the ALICE experiment

We present the results on two-particle Bose-Einstein correlations measured in proton-proton collisions at center of mass energies of sqrt{s}=0.9 TeV, sqrt{s}=2.76 TeV and sqrt{s}=7 TeV registered by the ALICE experiment at the Large Hadron Collider. Detailed analysis reveals that the three dimensional experimental correlation functions do not have Gaussian shape in two dimensions. We found that they are better described by an exponential functional form in the outward and longitudinal directions, while the sideward remains a Gaussian. This is interpreted as a result of a significant contribution of strongly decaying resonances to the shape of the emission region.

hep-ex↗