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At least 415 records · Page 23Linked to original sources
arXiv2013

Collective dynamics of the p-Pb collisions at the LHC

We review the signatures for the soft collective dynamics in highest-multiplicity ultrarelativistic p-Pb collisions and show that the effects are well described in a three-stage model, consisting of the event-by-event Glauber initial conditions, viscous 3+1D hydrodynamics, and statistical hadronization. In particular, we discuss the ridges in two-particle correlations in the relative azimuth and pseudorapidity, the elliptic and triangular flow coefficients, and the mass hierarchy of observables sensitive to flow.

nucl-th↗
arXiv2013

A new fission-fragment detector to complement the CACTUS-SiRi setup at the Oslo Cyclotron Laboratory

An array of Parallel Plate Avalanche Counters (PPAC) for the detection of heavy ions has been developed. The new device, NIFF (Nuclear Instrument for Fission Fragments), consists of four individual detectors and covers $60\%$ of 2$π$. It was designed to be used in conjunction with the SiRi array of $ΔE-E$ silicon telescopes for light charged particles and fits into the CACTUS array of 28 large-volume NaI scintillation detectors at the Oslo Cyclotron Laboratory. The low-pressure gas-filled PPACs are sensitive for the detection of fission fragments, but are insensitive to scattered beam particles of light ions or light-ion ejectiles. The PPAC detectors of NIFF have good time resolution and can be used either to select or to veto fission events in in-beam experiments with light-ion beams and actinide targets. The powerful combination of SiRi, CACTUS, and NIFF provides new research opportunities for the study of nuclear structure and nuclear reactions in the actinide region. The new setup is particularly well suited to study the competition of fission and $γ$ decay as a function of excitation energy.

nucl-ex↗
arXiv2013

Status of the NICA/MPD project

A general-purpose detector for studying heavy-ion collisions at the NICA facility is under construction at JINR. The NICA/MPD physics program, basic design requirements, and the MPD experimental setup will be described. Results of detector simulation and the expected performance for selected observables will be presented

nucl-ex↗
arXiv2013

Studies of exotic hadrons by high-energy exclusive reactions

We investigate the possibility of clarifying internal structure of exotic hadrons by high-energy exclusive reactions. In particular, the constituent-counting rule could be used for determining the internal configuration in large-angle exclusive scattering. As an example, we show the cross section pi^- + p -> K^0 + Lambda(1405) in comparison with the one for the ground-state Lambda production pi^- + p -> K^0 + Lambda. The counting rule indicates that the cross section scales as s^8 dsigma /dt=constant if Lambda(1405) is an ordinary three-quark baryon, whereas it is s^{10} dsigma /dt=constant if Lambda(1405) is a five-quark baryon. Here, s and t are Mandelstam variables. Such experiments could be possible at J-PARC, LEP, JLab, CERN-COMPASS, and other high-energy facilities.

hep-ph↗
arXiv2013

Deterministic Chaos in Radioactive Decay

We examine the radioactive decay of iodine in terms of its Kolmogorov entropy, observing a consistency with the presence of a regime of deterministic chaos in the vacuum dynamics.

nucl-ex↗
arXiv2013

Precise measurement of alpha-K for the 65.7-keV M4 transition in 119Sn: Extended test of internal-conversion theory

We have measured the K-shell internal conversion coefficient, alpha-K, for the 65.7-keV M4 transition in 119Sn to be 1621(25). This result agrees well with Dirac-Fock calculations in which the effect of the K-shell atomic vacancy is accounted for, and disagrees with calculations in which the vacancy is ignored. This extends our precision tests of theory to Z = 50, the lowest Z yet measured.

nucl-ex↗
arXiv2013

Radioactive contamination of BaF2 crystal scintillator

Barium fluoride (BaF$_2$) crystal scintillators are promising detectors to search for double beta decay processes in $^{130}$Ba ($Q_{2β}$ = 2619(3) keV) and $^{132}$Ba ($Q_{2β}$ = 844(1) keV). The $^{130}$Ba isotope is of particular interest because of the indications on 2$β$ decay found in two geochemical experiments. The radioactive contamination of BaF$_2$ scintillation crystal with mass of 1.714 kg was measured over 113.4 hours in a low-background DAMA/R&D set-up deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (LNGS, Italy). The half-life of $^{212}$Po (present in the crystal scintillator due to contamination by radium) was estimated as $T_{1/2}$ = 298.8 $\pm$ 0.8(stat.) $\pm$ 1.4(syst.) ns by analysis of the events pulse profiles.

nucl-ex↗
arXiv2014

GSI Oscillations as Laboratory for Testing of New Physics

We analyse recent experimental data on the GSI oscillations of the hydrogen-like heavy {^{142}}{\rm Pm}^{60+} ions that is a time modulation of the K-shell electron capture (EC) decay rate. We follow the mechanism of the GSI oscillations, caused by an interference of the neutrino flavour mass-eigenstates in a content of the electron neutrino. We give arguments that these experimental data show i) an existence of sterile neutrinos that is necessary for an explanation of a phase-shift, ii) an observation of CP violation, related to a phase-shift, and iii) an influence of the Quantum Zeno Effect, explaining different values of the amplitude and phase-shift for two runs of measurements with different time resolutions and different numbers of consecutive measurements.

hep-ph↗
arXiv2013

Fundamental Symmetry Tests with Nucleons, Nuclei, and Atoms: A Snowmass Report

Present and prospective fundamental symmetry tests with nucleons, nuclei and atoms are probing for possible new physics at the TeV scale and beyond. These ongoing and proposed table-top as well as accelerator-based experiments are thus a vital component of the Intensity Frontier. At the same time, these tests provide increasingly sophisticated probes of long-distance strong interactions that are responsible for the structure of nucleons and nuclei. In this community report, some of the most compelling opportunities with nucleons, nuclei and atoms are summarized, drawing largely on input received from the nuclear and atomic physics communities. In particular, this report includes many contributions submitted to two recent Intensity Frontier Workshops.

hep-ph↗
arXiv2013

ZDC Effective Cross Section for Run 12 Uranium-Uranium Collisions in RHIC

An accurate calibration of the luminosity measurement of the 2012 Uranium-Uranium RHIC run at 96 GeV per beam is of the greatest importance in order to measure the total uranium-uranium cross section with a reasonably small error bar. During the run, which lasted from April 20th to May 15th 2012, three vernier scans per experiment were performed. Beam intensities of up to 3.4 10$^{10}$ Uranium ions in one ring were successfully accelerated to flattop at $γ= 103.48$ corresponding to 96 GeV/beam. The desired model $β^*$ value was 0.7 m in the two low beta Interaction Points IP6 and IP8. With these beam parameters interaction rates of up to 15 kHz were achieved. This note presents the data associated with the vernier scans, and discusses the results and systematic effects.

physics.acc-ph↗
arXiv2013

Theoretical analysis of Lambda(1405) photoproduction

We develop a model that describes the gamma p -> K^+ pi Sigma reaction in the Lambda(1405) region. The model consists of gauge invariant photo-production mechanisms, and the chiral unitary model that gives the rescattering amplitudes where Lambda(1405) is contained. The model also contains phenomenological parameters, associated with short-range dynamics, to be used in fitting data. We successfully fit recent CLAS data for the pi-Sigma invariant mass distributions (line-shape) in the gamma p -> K^+ pi Sigma reaction for all the charge states. We find that the higher mass pole for Lambda(1405) of the chiral unitary model plays an important role in the reaction. We also find the non-resonant background contribution is not negligible, and its sizable effect shifts the Lambda(1405) peak position by several MeV. This work sets a starting point for a fuller analysis in which line-shape as well as K^+ angular distribution data are simultaneously analyzed for extracting Lambda(1405) pole(s).

nucl-th↗
arXiv2013

Measurements of Fission Products from the Fukushima Daiichi Incident in San Francisco Bay Area Air Filters, Automobile Filters, Rainwater, and Food

A variety of environmental media were analyzed for fallout radionuclides resulting from the Fukushima nuclear accident by the Low Background Facility (LBF) at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA. Monitoring activities in air and rainwater began soon after the onset of the March 11, 2011 tsunami and are reported here through the end of 2012. Observed fallout isotopes include $^{131}$I, $^{132}$I,$^{132}$Te,$^{134}$Cs, $^{136}$Cs, and $^{137}$Cs. Isotopes were measured on environmental air filters, automobile filters, and in rainwater. An additional analysis of rainwater in search of $^{90}$Sr is also presented. Last, a series of food measurements conducted in September of 2013 are included due to extended media concerns of $^{134, 137}$Cs in fish. Similar measurements of fallout from the Chernobyl disaster at LBNL, previously unpublished publicly, are also presented here as a comparison with the Fukushima incident. All measurements presented also include natural radionuclides found in the environment to provide a basis for comparison.

nucl-ex↗
arXiv2014

Using CMOS Sensors in a Cellphone for Gamma Detection and Classification

The CMOS camera found in many cellphones is sensitive to ionized electrons. Gamma rays penetrate into the phone and produce ionized electrons that are then detected by the camera. Thermal noise and other noise needs to be removed on the phone, which requires an algorithm that has relatively low memory and computational requirements. The continuous high-delta algorithm described fits those requirements. Only a small fraction of the energy of even the electron is deposited in the camera sensor, so direct methods of measuring the energy cannot be used. The fraction of groups of lit up pixels that are lines is correlated with the energy of the gamma rays. This correlation under certain conditions allows limited low resolution energy resolution to be performed.

physics.ins-det↗
arXiv2014

Letter of intent; Precise measurements of very forward particle production at RHIC

In this paper, we propose an experiment for the precise measurements of very forward particle production at RHIC. The proposal is to install a LHCf-like calorimeter in the ZDC installation slot at one of the RHIC interaction points. By installing a high-resolution electromagnetic calorimeter at this location we measure the spectra of photons, neutrons and pi0 at pseudo rapidity eta above 6. The new measurements at 500 GeV p-p collisions contribute to improve the hadronic interaction models used in the cosmic-ray air shower simulations. Using a similar kinematic coverage at RHIC to that of the measurements at LHC, we can test the Feynman scaling with a wide energy range and make the extrapolation of models into cosmic-ray energy more reliable. Combination of a high position resolution of the LHCf detector and a high energy resolution of the ZDC makes it possible to determine pT of forward neutrons with the ever best resolution. This enables us to study the forward neutron spin asymmetry discovered at RHIC in more detail. Another new experiment expected at RHIC is world-first light-ion collisions. Cosmic-ray interaction models have been so far tested with accelerator data, but colliders have provided only p-p and heavy-ion collisions. To simulate the interaction between cosmic-ray particles and atmosphere, collision of light ions like nitrogen is a ultimate goal for the cosmic-ray physics. We propose 200 GeV p-N collisions together with 200 GeV p-p collisions to study the nuclear effects in the forward particle production. The experiment can be performed by using the existing LHCf detector. Considering the geometry and response of one of the LHCf detectors, we propose some short dedicated operations. Ideal beam conditions are summarized in this paper. Our basic idea is to bring one of the LHCf detectors to RHIC and then operate from 2016 season at RHIC.

physics.ins-det↗
arXiv2014

The width of the $ω$ meson in dense matter

We obtain the width of the $ω$ meson in dense nuclear matter by taking into account (i) the free decay of the $ω$ into three pions, which is dominated by $ρπ$ mode, (ii) the processes induced by a vector-baryon interaction dominated by vector meson exchange, and (iii) the $ω\to K \bar K$ mechanism in matter. The $ω$ meson develops an important width in matter, coming from the dominant $ω\to ρπ$ decay mode, with a value of $121 \pm 10$ MeV at normal nuclear matter density for an $ω$ at rest. At finite momentum, the width of the $ω$ meson increases moderately with values of 200 MeV at 600 MeV/c.

nucl-th↗
arXiv2014

NLO QCD corrections for DVCS and TCS

The inclusion of QCD corrections to the Born amplitude of deeply virtual Compton scattering in both spacelike (DVCS) and timelike (TCS) regimes modifies the extraction process of generalized parton distributions (GPDs) from observables. In particular, gluon contributions are by no means negligible even in the medium energy range accessible at JLab12. We emphasize the complementarity of spacelike and timelike measurements and raise the question of factorization scale dependence of the O(alpha_S) results.

hep-ph↗
arXiv2014

Comments concerning the paper "Measurement of negatively charged pion spectra in inelastic p+p interactions at 20, 31, 40, 80 and 158 GeV/c" by the NA61 collaboration

New data from the NA61 collaboration on the production of negative pions in p+p interactions at beam momenta between 20 and 158 GeV/c are critically compared to available results in the same energy range. It is concluded that the NA61 data show some discrepancies with the previous results. This concerns in particular the total yields, the $p_T$ integrated rapidity distributions and the double differential cross sections.

hep-ex↗