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At least 19 recordsLinked to original sources

arXiv2007

Strange Nucleon Form Factors from $ep$ and $νp$ Elastic Scattering

The recent parity-violating $ep$ forward-scattering elastic asymmetry data from Jefferson Lab (HAPPEx and G0), when combined with the $νp$ elastic cross section data from Brookhaven (E734), permit an extraction of the strangeness contribution to the vector and axial nucleon form factors for momentum transfers in the range $0.45 < Q^2 < 1.0$ GeV$^2$. These results, combined with the recent determination of the strange vector form factors at $Q^2 = 0.1$ GeV$^2$ (SAMPLE, HAPPEx, PVA4, G0) have been interpreted in terms of $uuds\bar{s}$ configurations very different from the kaon-loop configurations usually associated with strangeness in the nucleon. New experiments are being proposed to improve the state of our knowledge of the $νp$ elastic cross section -- these new experiments will push the range of $Q^2$ to much lower values, and greatly increase the precision of the $νp$ elastic data. One outcome of this can be a measurement of the strangeness contribution to the nucleon spin, $Δs$. Nuclear targets (e.g. C or Ar) are to be used in these neutrino experiments, and so a deep understanding of the nuclear physics, particularly in regard to final state effects, is needed before the potential of these precision experiments can be fully realized.

hep-ex↗

arXiv2007

Search for color charge dependence of energy loss at RHIC

The non-Abelian feature of quantum chromodynamics (QCD) results in the gluons losing more energy than quarks in the medium formed in high energy heavy-ion collisions. Experimental results in p+p collisions when compared to NLO pQCD calculations show that at high transverse momentum (pT) the produced protons+anti-protons are dominantly from gluon jets and charged pions have substantial contribution from quark jets. If such a scenario is applied to heavy-ion collisions at RHIC, one would expect the difference in quark and gluon energy loss to have an effect on measured observables, such as high pT pbar(p)/pi ratios and the nuclear modification factor for various particles species. We discuss the experimental results and some possible future measurements.

nucl-ex↗

arXiv2007

Neutronic performances of the MEGAPIE target

The MEGAPIE project is a key experiment on the road to Accelerator Driven Systems and it provides the scientific community with unique data on the behavior of a liquid lead-bismuth spallation target under realistic and long term irradiation conditions. The neutronic of such target is of course of prime importance when considering its final destination as an intense neutron source. This is the motivation to characterize the inside neutron flux of the target in operation. A complex detector, made of 8 micro fission-chambers, has been built and installed in the core of the target, few tens of centimeters from the proton/Pb-Bi interaction zone. This detector is designed to measure the absolute neutron flux inside the target, to give its spatial distribution and to correlate its temporal variations with the beam intensity. Moreover, integral information on the neutron energy distribution as a function of the position along the beam axis could be extracted, giving integral constraints on the neutron production models implemented in transport codes such as MCNPX.

nucl-ex↗

arXiv2007

Measurement of electro-magnetic radiation at PHENIX

Recent results on direct photons and dileptons from the PHENIX xperiment opened up a possibility of landscaping electro-magnetic radiation over various kinetic energies in heavy ion collisions. A detail discussion is given based on a review of the results.

nucl-ex↗

arXiv2007

Is the Pentaquark the Only Justification for Research on KN Physics ?

The talk is intended to motivate the use of DA$Φ$NE--2 running at the $ϕ$ peak as an intense, clean source of low--momentum charged and neutral kaons. It covers a few open problems still unsolved after more than twenty--five years and the physics (some of it still novel) that could be learned only in this way. And, of course, the answer to the above question is {\sl NO}.

nucl-th↗

arXiv2007

Heavy ion physics with the ALICE experiment at LHC

ALICE is the experiment at the LHC collider at CERN dedicated to heavy ion physics. In this report, the ALICE detector will be presented, together with its expected performance as far as some selected physics topics are concerned.

nucl-ex↗

arXiv2007

Mapping out the Jet correlation landscape: Jet quenching and Medium response

A selected set of di-hadron correlation results from PHENIX are discussed. These results provide evidences for four distinct contributions concentrated at various $Δϕ$ ranges. The $p_T$, particle species and energy dependence of these contributions reflect detailed interplay between jet quenching and response of the partonic matter to the lost energy.

nucl-ex↗

arXiv2008

Simulation of symmetric nuclei and the role of Pauli potential in binding energies and radii

It is shown that the use of a density dependent effective Pauli potential together with a nucleon-nucleon interaction potential plays a crucial role to reproduce not only the binding energies but also the matter root mean square radii of medium mass range spin-isospin saturated nuclei. This study is performed with a semiclassical Monte Carlo many-body simulation within the context of a simplified nucleon-nucleon interaction to focus on the effect of the genuine correlations due to the fermionic nature of nucleons. The procedure obtained is rather robust and it does not depend on the detailed features of the nucleon-nucleon interaction. For nuclei below saturation the density dependence may be represented in terms either of the nucleon number, $A$, or the associated Fermi momenta. When testing the simulation procedure for idealized "infinite" symmetric nuclear matter within the corresponding range of densities, it turns out that finite size effects affect the Pauli potential strength parametrization in systems up to about 120 particles while remaining approximately stable for larger systems.

nucl-th↗

arXiv2007

First performance studies of a prototype for the CASTOR forward calorimeter at the CMS experiment

We present results on the performance of the first prototype of the CASTOR quartz-tungsten sampling calorimeter, to be installed in the very forward region of the CMS experiment at the LHC. This study includes GEANT Monte Carlo simulations of the Cherenkov light transmission efficiency of different types of air-core light guides, as well as analysis of the calorimeter linearity and resolution as a function of energy and impact-point, obtained with 20-200 GeV electron beams from CERN/SPS tests in 2003. Several configurations of the calorimeter have been tested and compared, including different combinations of (i) structures for the active material of the calorimeter (quartz plates and fibres), (ii) various light-guide reflecting materials (glass and foil reflectors) and (iii) photodetector devices (photomultipliers and avalanche photodiodes).

physics.ins-det↗

arXiv2007

Experimental tests of small-x QCD

Current and future experimental studies of the high-energy limit of QCD, dominated by non-linear gluon dynamics in the low-x sector of the hadron wavefunctions, are presented. Results at HERA (proton) and RHIC (nucleus) pointing to the possible onset of parton saturation phenomena, and perspectives at the LHC and new proposed DIS facilities are outlined.

hep-ex↗

arXiv2007

Search for Low Mass Exotic leptonic or bosonic structures

Recently, several papers discussed the existence of a low mass leptonic structure. It was suggested that the $Σ^{+}$ disintegration: $Σ^{+}\to$pP$^{0}$, P$^{0}\toμ^{-}μ^{+}$ proceeds through an intermediate particle P$^{0}$ having a mass close to M$\approx$~214.3 MeV. The present work intends to look at other available data, in order to observe the eventual existence of a small peak or shoulder, at a mass close to M=214.3 MeV, which can strengthen the existence of a state produced by two leptons of opposite electric charge.

nucl-ex↗

arXiv2007

Hard-scattering and Jets from RHIC to LHC: a critical review

Jets in hadron collisions are very complicated with a long learning curve replete with errors. In relativistic heavy ion (RHI) collisions, it is likely that jets will be much more complicated with an even longer and more difficult learning curve. Hard scattering is more easily observed via single particle and few particle correlation measurements. The main advantage of jets is higher rate at large $p_T$, plus the possibility of detailed studies of soft fragmentation if the soft fragments can be separated from the background. A critical review of the possibility of using jets as a probe of hard-scattering in RHI collisions is presented along with other probes and measurements which the author considers much more likely to reveal the interesting physics in Pb+Pb collisions at the LHC. Finally, a list of unanswered questions raised by results at RHIC is presented.

nucl-ex↗

arXiv2007

Double beta decay: experiments and theory review

Neutrinoless double beta decay is one of the most powerful tools to set the neutrino mass absolute scale and establish whether the neutrino is a Majorana particle. After a summary of the neutrinoless double beta decay phenomenology, the present status of the experimental search for this rare decay is reported and the prospects for next generation experiments are reviewed.

nucl-ex↗

arXiv2007

Particle production mechanisms from RHIC to LHC

I will review RHIC data with respect to the intriguing possibility that the hadron production mechanism in the produced partonic medium might be different than in vacuum. I will use the measurements of collective features, such as flow and quenching of identified particles, to show that different regions of the particle momentum spectrum are likely populated through different mechanisms, and that the medium seems to play an important role in hadronization. Finally I will address the question whether the different initial conditions achievable in heavy ion collisions at LHC energies, compared to RHIC, might affect the properties of the deconfined quark-gluon phase and its hadronization to baryonic matter.

nucl-ex↗

arXiv2007

Forward Physics at the LHC

Small-angle detectors at the LHC give access to a broad physics programme within and beyond the Standard Model (SM). We review the capabilities of ALICE, ATLAS, CMS, LHCb, LHCf and TOTEM for forward physics studies in various sectors: soft and hard diffractive processes, exclusive Higgs production, low-x QCD, ultra-high-energy cosmic-rays, and electro-weak measurements.

hep-ex↗

arXiv2007

Modeling Atmospheric Neutrino Interactions: Duality Constrained Parameterization of Vector and Axial Nucleon Form Factors

We present new parameterizations of vector and axial nucleon form factors. We maintain an excellent descriptions of the form factors at low momentum transfers, where the spatial structure of the nucleon is important, and use the Nachtman scaling variable ξto relate elastic and inelastic form factors and impose quark-hadron duality constraints at high momentum transfers where the quark structure dominates. We use the new vector form factors to re-extract updated values of the axial form factor from neutrino experiments on deuterium. We obtain an updated world average value from neutrino and pion electroproduction experiments of M_A = 1.0144 +- 0.0136 GeV/c2. Our parameterizations are useful in modeling atmospheric neutrino interactions (e.g. for neutrino oscillations experiments)

hep-ex↗

arXiv2007

Collective flow in heavy ion collisions at intermediate energies

We present results of a flow analysis for the set of reactions of 124,129Xe projectiles and 112,124Sn targets at incident energies 100 and 150 A MeV studied with the INDRA detector at GSI. The dependence on centrality and on p_t of the directed and elliptic flow are determined for isotopically selected reaction products with Z \le 3. The flow parameters v_1 and v_2, in general, follow expected trends but isotopic effects are small.

nucl-ex↗

arXiv2008

An estimate for the location of QCD critical end point

It is proposed that a study of the ratio of shear viscosity to entropy density $\fracη{s}$ as a function of the baryon chemical potential $μ_B$, and temperature T, provides a dynamic probe for the critical end point (CEP) in hot and dense QCD matter. An initial estimate from an elliptic flow excitation function gives $μ^{\text{cep}}_B \sim 150-180$ MeV and $T_{\text{cep}} \sim 165 - 170$ MeV for the location of the the CEP. These values place the CEP in the range for "immediate" validation at RHIC.

nucl-ex↗