arXiv subjects

E. Norbeck

Publications and source records attributed to E. Norbeck.

33 records · Page 2Linked to original sources

arXiv2010

Multifragmentation in Collisions of 4.4gev-Deuterons with Gold Target

The relative velocity correlation function of pairs of intermediate mass fragments has been studied for d+Au collitions at 4.4 GeV. Experimental correlation functions are compared to that obtained by multibody Coulomb trajectory calculations under the assumption of various decay timees of the fragmenting system. The combined approach with the empirically modified intranuclear cascade code followed by the statistical multifragmentation model was used to generate the starting conditions for these calculations. The fragment emossion time is found to be less than 40 fm/c.

nucl-ex↗

arXiv2009

Forward Physics with Rapidity Gaps at the LHC

A rapidity gap program with great potential can be realized at the Large Hadron Collider, LHC, by adding a few simple forward shower counters (FSCs) along the beam line on both sides of the main central detectors, such as CMS. Measurements of single diffractive cross sections down to the lowest masses can be made with an efficient level-1 trigger. Exceptionally, the detectors also make feasible the study of Central Diffractive Excitation, and in particular the reaction g + g to g + g, in the color singlet channel, effectively using the LHC as a gluon-gluon collider.

hep-ex↗

arXiv2009

Measurement of the Rate Capability of Resistive Plate Chambers

This paper reports on detailed measurements of the performance of Resistive Plate Chambers in a proton beam with variable intensity. Short term effects, such as dead time, are studied using consecutive events. On larger time scales, for various beam intensities the chamber.s efficiency is studied as a function of time within a spill of particles. The correlation between the efficiency of chambers placed in the same beam provides an indication of the lateral size of the observed effects. The measurements are compared to the predictions of a simple model based on the assumption that the resistive plates behave as pure resistors.

physics.ins-det↗

arXiv2008

Calibration of a digital hadron calorimeter with muons

The calibration procedure of a finely granulated digital hadron calorimeter with Resistive Plate Chambers as active elements is described. Results obtained with a stack of nine layers exposed to muons from the Fermilab test beam are presented.

physics.ins-det↗

arXiv2008

Critical temperature for the nuclear liquid-gas phase transition (from multifragmentation and fission)

Critical temperature Tc for the nuclear liquid-gas phase transition is stimated both from the multifragmentation and fission data. In the first case,the critical temperature is obtained by analysis of the IMF yields in p(8.1 GeV)+Au collisions within the statistical model of multifragmentation (SMM). In the second case, the experimental fission probability for excited 188Os is compared with the calculated one with Tc as a free parameter. It is concluded for both cases that the critical temperature is higher than 16 MeV.

nucl-ex↗

arXiv2007

Measuring Photons and Neutrons at Zero Degrees in CMS

The CMS Zero Degree Calorimeters, ZDCs, will measure photons and neutrons emitted with |eta|> 8.6 from Pb+Pb, p+Pb and p+p collisions at sqrt(Snn)=5.5, 8.8 and 14 TeV respectively. The calorimeter consists of an electromagnetic part segmented in the horizontal direction and an hadronic part segmented into four units in depth. In addition CMS will have access to data from a segmented shower maximum detector being built for luminosity measurements. We will present detailed results from tests beam measurements taken at the CERN SPS. These data will be used to extrapolate the utility of the ZDCs to measure photons, and possibly pi0s in p+p and ultra-peripheral heavy-ion collisions. Data from the hadronic section can be used to estimate the number of participants in heavy ion-collisions. In addition we will discuss plans to use the detector to measure the reaction plane, thereby extending the sensitivity of the central detectors in CMS.

nucl-ex↗

arXiv2006

Status of Zero Degree Calorimeter for CMS Experiment

The Zero Degree Calorimeter (ZDC) is integral part of the CMS experiment, especially, for heavy ion studies. The design of the ZDC includes two independent calorimeter sections: an electromagnetic section and a hadronic section. Sampling calorimeters using tungsten and quartz fibers have been chosen for the energy measurements. An overview of the ZDC is presented along with a current status of calorimeter's preparation for Day 1 of LHC.

nucl-ex↗

arXiv2006

Time scale of the thermal multifragmentation in p(3.6 GeV) + Au collisions

The relative angle correlation of intermediate mass fragments has been studied for p+Au collisions at 3.6 GeV. Strong suppression at small angles is observed caused by IMF-IMF Coulomb repulsion. Experimental correlation function is compared to that obtained by the multi-body Coulomb trajectory calculations with the various decay time of fragmenting system. The combined model including the empirically modified intranuclear cascade followed by statistical multifragmentation was used to generate starting conditions for these calculations. The model dependence of the results obtained has been carefully checked. The mean decay time of fragmenting system is found to be 85 +- 50 fm/c.

nucl-ex↗

arXiv2006

Nuclear multifragmentation and fission: similarity and differences

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid--fog phase transition deep inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed. It is concluded that the decay process of hot nuclei is characterized by two size parameters: transition state and freeze-out volumes. The similarity between dynamics of fragmentation and ordinary fission is discussed. The IMF emission time is related to the mean rupture time at the multi-scission point, which corresponds to the kinetic freeze-out configuration.

nucl-ex↗

arXiv2004

Spinodal decomposition, nuclear fog and two characteristic volumes in thermal multifragmentation

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition inside the spinodal region. The experimental data for p(8.1GeV) + Au collisions are analyzed within the framework of the statistical multifragmentation model (SMM) for the events with emission of at least two IMFs. It is found that the partition of hot nuclei is specified after expansion to a volume equal to Vt = (2.6+-0.3) Vo, with Vo as the volume at normal density. However, the freeze-out volume is found to be twice as large: Vf = (5+-1) Vo.

nucl-ex↗

arXiv2004

Two characteristic volumes in thermal nuclear multifragmentation

The paper is devoted to the experimental determination of the space-time characteristics for the target multifragmentation in p(8.1GeV) + Au collisions. The experimental data on the fragment charge distribution and kinetic energy spectra are analyzed within the framework of the statistical multifragmentation model. It is found that the partition of hot nuclei is specified after expansion of the target spectator to a volume equal to Vt = (2.9 +- 0.2) Vo, with Vo as the volume at normal density. However, the freeze-out volume is found to be Vf = (11 +- 3) Vo. At freeze-out, all the fragments are well separated and only the Coulomb force should be taken into account. The results are in accordance with a scenario of spinodal disintegration of hot nuclei.

hep-ex↗

arXiv2003

Multifragmentation and nuclear phase transitions (liquid-fog and liquid-gas)

Thermal multifragmentation of hot nuclei is interpreted as the nuclear liquid-fog phase transition. The charge distributions of the intermediate mass fragments produced in p(3.6 GeV) + Au and p(8.1 GeV) + Au collisions are analyzed within the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition Tc as a free parameter. The analysis presented here provides strong support for a value of Tc > 15 MeV.

nucl-ex↗

arXiv2003

Critical Temperature for the Nuclear Liquid-Gas Phase Transition

The charge distribution of the intermediate mass fragments produced in p (8.1 GeV) + Au collisions is analyzed in the framework of the statistical multifragmentation model with the critical temperature for the nuclear liquid-gas phase transition $T_c$ as a free parameter. It is found that $T_c=20\pm3$ MeV (90% CL).

nucl-ex↗

arXiv2002

Comparative Study of Multifragmentation of Gold Nuclei Induced by Relativistic Protons, $^4$He, and $^{12}$C

Multiple emission of intermediate-mass fragments has been studied for the collisions of p, $^4$He and $^{12}$C on Au with the $4π$ setup FASA. The mean IMF multiplicities (for the events with at least one IMF) are saturating at the value of $2.2\pm0.2$ for the incident energies above 6 GeV. The observed IMF multiplicities cannot be described in a two-stage scenario, a fast cascade followed by a statistical multifragmentation. Agreement with the measured IMF multiplicities is obtained by introducing an intermediate phase and modifying empirically the excitation energies and masses of the remnants. The angular distributions and energy spectra from the p-induced collisions are in agreement with the scenario of ``thermal'' multifragmentation of a hot and diluted target spectator. In the case of $^{12}$C+Au(22.4 GeV) and $^4$He(14.6 GeV)+Au collisions, deviations from a pure thermal break-up are seen in the energy spectra of the emitted fragments, which are harder than those both from model calculations and from the measured ones for p-induced collisions. This difference is attributed to a collective flow.

nucl-ex↗

arXiv2001

Transition from Thermal to Rapid Expansion in Multifragmentation of Gold Induced by Light Relativistic Projectiles

Multiple emission of intermediate-mass fragments has been studied for the collisions of p, $^4$He and $^{12}$C on Au with the $4π$ setup FASA. In the case of $^{12}$C(22.4 GeV)+Au and $^4$He(14.6 GeV)+Au collisions, the deviations from a pure thermal break-up are seen in the energy spectra of the emitted fragments: the spectra are harder than calculated and than measured in p-induced collisions. This difference is attributed to a collective flow with the expansion velocity on the surface about 0.1 $c$ (for $^{12}$C+Au collisions).

nucl-ex↗