Absorption Of Hadrons Research Articles

Transverse-momentum dependent model for hadronization in deep-inelastic lepton-nucleus scattering off heavy nuclei

Semi-inclusive deep inelastic scattering off nuclei is a unique process to study the parton propagation mechanism and its modification induced by the presence of the nuclear medium. It allows us to probe the medium properties, particularly the cold nuclear matter transport coefficient, which can be directly linked to the nuclear gluon density. We present here a model for hadron production in deep inelastic lepton-nucleus scattering, which takes into account the hadronic transverse momentum of final state particles via transverse-momentum dependent parton distributions and fragmentation functions. We implement parton energy loss and hadronic absorption with a geometrical model of the nucleus. The model is compared with the nuclear semi-inclusive deep-inelastic scattering multiplicity ratios and transverse-momentum broadening data from the CLAS, HERMES, and EMC collaborations, aiming for a simultaneous description of these data sets. We obtain a good agreement over the various nuclear targets and the wide kinematical range of those experiments. We best describe the data with a transport coefficient q̂=0.3GeV/fm2, and we highlight the importance and the role of correlations in extracting this quantity. Published by the American Physical Society 2024

Measurement of charged-pion production in deep-inelastic scattering off nuclei with the CLAS detector

Background: Energetic quarks in nuclear deep-inelastic scattering propagate through the nuclear medium. Processes that are believed to occur inside nuclei include quark energy loss through medium-stimulated gluon bremsstrahlung and intranuclear interactions of forming hadrons. More data are required to gain a more complete understanding of these effects. Purpose: To test the theoretical models of parton transport and hadron formation, we compared their predictions for the nuclear and kinematic dependence of pion production in nuclei. Methods: We have measured charged-pion production in semi-inclusive deep-inelastic scattering off D, C, Fe, and Pb using the CLAS detector and the CEBAF 5.014-GeV electron beam. We report results on the nuclear-to-deuterium multiplicity ratio for π+ and π− as a function of energy transfer, four-momentum transfer, and pion energy fraction or transverse momentum—the first three-dimensional study of its kind. Results: The π+ multiplicity ratio is found to depend strongly on the pion fractional energy z and reaches minimum values of 0.67±0.03, 0.43±0.02, and 0.27±0.01 for the C, Fe, and Pb targets, respectively. The z dependencies of the multiplicity ratios for π+ and π− are equal within uncertainties for C and Fe targets but show differences at the level of 10% for the Pb-target data. The results are qualitatively described by the GiBUU transport model, as well as with a model based on hadron absorption, but are in tension with calculations based on nuclear fragmentation functions. Conclusions: These precise results will strongly constrain the kinematic and flavor dependence of nuclear effects in hadron production, probing an unexplored kinematic region. They will help to reveal how the nucleus reacts to a fast quark, thereby shedding light on its color structure and transport properties and on the mechanisms of the hadronization process.Received 25 September 2021Accepted 23 December 2021DOI:https://doi.org/10.1103/PhysRevC.105.015201©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasColor confinementDeep inelastic scatteringLepton induced nuclear reactionsParticle interactionsParticle productionQuantum chromodynamicsStrong interactionNuclear PhysicsParticles & Fields

Strong Absorption of Hadrons with Hidden and Open Strangeness in Nuclear Matter.

We present the first observation of K^{-} and ϕ absorption within nuclear matter by means of π^{-}-induced reactions on C and W targets at an incident beam momentum of 1.7 GeV/c studied with HADES at SIS18/GSI. The double ratio (K^{-}/K^{+})_{W}/(K^{-}/K^{+})_{C} is found to be 0.319±0.009(stat)_{-0.012}^{+0.014}(syst) indicating a larger absorption of K^{-} in heavier targets as compared to lighter ones. The measured ϕ/K^{-} ratios in π^{-}+C and π^{-}+W reactions within the HADES acceptance are found to be equal to 0.55±0.04(stat)_{-0.07}^{+0.06}(syst) and to 0.63±0.06(stat)_{-0.11}^{+0.11}(syst), respectively. The similar ratios measured in the two different reactions demonstrate for the first time experimentally that the dynamics of the ϕ meson in nuclear medium is strongly coupled to the K^{-} dynamics. The large difference in the ϕ production off C and W nuclei is discussed in terms of a strong ϕN in-medium coupling. These results are relevant for the description of heavy-ion collisions and the structure of neutron stars.

Investigation of abnormal absorption of cosmic-ray hadrons in lead calorimeters

A phenomenon of abnormally weak absorption of very high energy cosmic ray hadrons in thick lead blocks is discussed. This phenomenon was first observed in a Tien Shan high altitude experiment to study hadronic cores of extensive air showers (EAS) with a deep ionization calorimeter and encouraged researchers to introduce the hypothesis of the so-called long-flying or penetrating cosmic ray component. A similar effect was detected later with deep uniform lead X-ray emulsion chambers (XREC) at the Pamirs, which we discuss in detail. To establish the nature of the phenomenon we are have carried out dedicated experiments at the Tien Shan and at the Pamirs by exposing two-storey XRECs with large air gaps. According to detailed simulation of the chamber response, these experiments are very sensitive to the production of charmed hadrons in the forward kinematic region and can prove a hypothesis that the phenomenon under study can be explained on the assumption of very high values of charm particle production cross section at 〈ELab〉 ~ 75 TeV in the forward kinematic region at xLab≳ 0.1 which are near the upper limit of recent results of collider experiments, i.e., σpp→c¯c~ 8 mb. The same factor makes it possible to fit all the features of the experimental hadron absorption curve observed by means of deep uniform lead XRECs, including its bending at a depth of ~ 70 c.u.

Hadronic absorption cross sections ofBc

The cross sections of $B_{c}$\ absorption by $\pi $ mesons are calculated using hadronic Lagrangian based on SU(5) flavor symmetry. Calculated cross sections are found to be in range 2 to 7 mb and 0.2 to 2 mb for the processes $B_{c}^{+}\pi \rightarrow DB$ and $B_{c}^{+}\pi \rightarrow D^{\ast}B^{\ast}$ respectively, when the monopole form factor is included. These results could be useful in calculating production rate of $B_{c}$ meson in relativistic heavy ion collisions.

ϒ production in p+p, d+Au, Au+Au collisions at [formula omitted] in STAR

Quarkonium is a good probe of the dense matter produced in heavy-ion collisions at RHIC because it is produced early in the collision and the production is theorized to be suppressed due to the Debye color screening of the potential between the heavy quarks. A model dependent measurement of the temperature of the Quark Gluon Plasma (QGP) can be made by examining the ratio of the production of various quarkonium states in heavy ion collisions versus p+p collisions as lattice calculations indicate that the quarkonium states will be sequentially suppressed. Suppression is quantified by calculating R A A , which is the ratio of the yield in Au+Au to the production in p+p scaled by the number of binary collisions. The ϒ states are of particular interest because at 200 GeV the effects of feed down and co-movers are smaller than for J / ψ which decreases the systematic uncertainty of the R A A determination. In addition to hadronic absorption, additional cold nuclear matter effects, such as shadowing of the PDFs, can be determined from d+Au collisions. We will present our results for mid-rapidity ϒ production in p+p, as well as our preliminary results in d+Au and Au+Au at s = 200 GeV . These results will then be compared with theoretical QCD calculations.

Hadronic absorption cross sections of Bc

The absorption cross sections B c meson by hadronic commoving systems (nucleons) are investigated using a gauged SU 5 hadronic Lagrangian in mesonic exchange model. The energy dependence of dissociation cross sections are calculated from the threshold to higher energies with monopole form factor. Depending on values of the monopole form factor cut off parameter used, the peak cross sections are found significantly large. We present this analysis for the form factor and coupling constants used in calculating the B c dissociation cross sections.

Can We Distinguish Energy Loss from Hadron Absorption?

Knowing whether a hadron is formed inside or outside the nuclear medium is very important for correctly interpreting jet quenching in heavy-ion collisions. The cleanest experimental environment to study the space-time evolution of hadronization is semi-inclusive DIS on nuclear targets. 2 frameworks are presently competing to explain the observed attenuation of hadron production: quark energy loss, with hadron formation outside the nucleus [2, 3], and nuclear absorption with hadronization starting inside the nucleus [4–6]. I demonstrate that the observed approximate A2/3 scaling of experimental data cannot conclusively establish the correctness of either energy loss or absorption.

Low momentum muon identification in the ATLAS detector at the LHC

Muon identification and high momentum measurement accuracy are crucial to fully exploit the physics potential of the ATLAS experiment at the LHC. The muon detection system of the ATLAS detector is characterized by two high precision tracking systems, namely the Inner Detector and the Muon Spectrometer, and sufficient calorimetry to ensure the safe absorption of hadrons before the spectrometer, yielding high purity muons with momenta above 3 GeV. In order to reconstruct and efficiently identify muon tracks, the MOORE and MuId Object-Oriented software packages have been developed within the ATLAS ATHENA framework. The MOORE and MuId algorithms combine to identify track segments in the Muon Spectrometer, exploit calorimeter information in order to extrapolate muons back to their production vertex, associate them with corresponding segments in the Inner Detector, and perform a combined fit to obtain optimal parameter resolution. To identify low pT muons that do not have a reconstructed Muon Spectrometer track, other strategies must be employed. We report on a method we developed to identify low pT muons and describe the offline performance studies. The simplicity of the algorithm renders it suitable for use in the ATLAS High-Level Trigger (HLT) system. We will discuss the adaptation of this algorithm for the Level Two Trigger.

A muon identification and combined reconstruction procedure for the ATLAS detector at the LHC at CERN

Muon identification and high momentum measurement accuracy is crucial to fully exploit the physics potential that will be accessible with ATLAS experiment at the LHC. The muon energy of physics interest ranges in a large interval from few GeV, where the b-physics studies dominate the physics program, up to the highest values that could indicate the presence of new physics. The muon detection system of the ATLAS detector is characterized by two high precision tracking systems, namely the Inner Detector and the Muon Spectrometer plus a thick calorimeter that ensures a safe hadron absorption filtering with high purity muons with energy above 3 GeV. In order to combine the muon tracks reconstructed in the Inner Detector and the Muon Spectrometer the Muon Identification (MUID) Object-Oriented software package has been developed. The purpose of the MUID procedure is to associate tracks found in the Muon Spectrometer with the corresponding Inner Detector track and calorimeter information in order to identify muons at their production vertex with optimum parameter resolution. The performance of these two combined systems has been evaluated with single muons of fixed transverse momentum and with full physics events.

Hadron suppression in DIS at HERMES

The influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi-inclusive deep-inelastic scattering of 27.6 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity for krypton relative to that of deuterium has been measured for the first time for various identified hadrons (π+, π−, π0, K+, K−, p and ) as a function of the virtual photon energy ν, the fraction z of this energy transferred to the hadron, and the hadron transverse momentum squared p2t. The distribution of the hadron transverse momentum is broadened towards high p2t in the nuclear medium, in a manner resembling the Cronin effect previously observed in collisions of heavy ions and protons with nuclei. Moreover, by studying the hadron attenuation of the leading and sub-leading hadrons, we report, for the first time, the possibility of better disentangling between the hadron absorption and the energy loss contribution.

Hadron production in deep inelastic lepton–nucleus scattering

Predictions for semi-inclusive deep inelastic lepton–nucleus scattering are presented. Both the effects of gluon radiation by the struck quark and the absorption of the produced hadron are considered. The gluon radiation covers a larger window in virtuality Q 2 because of the increased deconfinement of quarks inside nuclei. The absorption of hadrons formed inside the nucleus is described with a flavor dependent cross-section. Calculations for rescaled fragmentation functions and nuclear absorption are compared with the EMC and HERMES data for N, Cu and Kr targets with respect to the deuteron target. Predictions for Ne and Xe targets in the HERMES kinematic regime are given.

J/ψsuppression in ultrarelativistic nuclear collisions

Using a multiphase transport model, we study the relative importance of J/psi suppression mechanisms due to plasma screening, gluon scattering, and hadron absorption in heavy ion collisions at the Relativistic Heavy Ion Collider. We find that for collisions between heavy nuclei such as Au+Au, both plasma screening and gluon scattering are important. As a result, the effect due to absorption by hadrons becomes relatively minor. The final J/psi survival probability in these collisions is only a few percent. In the case of collisions between light nuclei such as S+S, the effect of plasma screening is, however, negligible in spite of the initial high parton density. The final J/psi survival probability thus remains appreciable after comparable absorption effects due to gluons and hadrons.

Role of gluon depletion in J/ψ suppression

The depletion of gluons as the parton flux traverses a nucleus in a heavy-ion collision can influence the production rate of heavy-quark states. Thus the suppression of J/{psi} can be due to gluon depletion in the initial state in addition to nuclear and hadronic absorption in the final state. A formalism is developed to describe the depletion effect. It is shown that, without constraints from other experimental facts beside the J/{psi} suppression data in pA and AB collisions, it is not possible to determine the relative importance of depletion vs absorption. Possible relevance to the enhanced suppression seen in the Pb-Pb data is mentioned but not studied. {copyright} {ital 1997} {ital The American Physical Society}

Initial state effects on dilepton production in nuclear collisions

For hadron-nucleus collisions, multiple elastic scattering of the incident parton inside the nucleus leads to a broadening of the PT distribution for high mass dilepton production. Such a broadening has been used to explain the PT-dependence of the J/ψ suppression observed in high energy O — U and S — U collisions. Precision measurements of the A-dependence of dilepton distributions from h — A collisions can provide a test of this explanation. Furthermore, a comparison of the PT-dependence of J/ψ and Drell-Yan production in nucleus-nucleus collisions, as a function of ET, can be used to distinguish between quark deconfinement and hadronic absorption as the origin of the observed J/ψ suppression.

Initial state effects on dilepton production in nuclear collisions

For hadron-nucleus collisions, multiple elastic scattering of the incident parton inside the nucleus leads to a broadening of the p t distribution of high mass dilepton production. Such a broadening has been used to explain the p t dependence of the J/ ψ suppression observed in high energy O - U and S - U collisions. Precision measurements of the A-dependence of dilepton distributions from h - A collisions can provide a test of this explanation. Furthermore, a comparison of the P T -dependence of J/ ψ and Drell-Yan production in nucleus-nucleus collisions, as function of E T -can be used to distinguish between quark deconfinement and hadronic absorption as origin of the observed J/ ψ suppression.

Weakening of string tension and charmonium suppression

Effects of survival probability and hadronic absorption in hydrodynamical development of quark gluon plasma are discussed in a frame work of a kinetic equation.

Quark-gluon plasma radiography by mesons with hidden favour

Measurement of the ratio of the Phi and J/ Psi mesons as a function of multiplicity is proposed as a tool to observe quark-gluon plasma formation in relativistic heavy-ion collisions. The effect of the hadronic absorption on this ratio is analysed.

Characteristics of hadronic showers detected by Cherenkov radiation in lead glass

Spatial and energy characteristics of hadron showers were studied for the first time with the help of a total hadron absorption detector made from lead glass. The calorimeter model having a longitudinal and transverse hodoscopic structure with 10 cm step width is exposed to a particle beam of e +, μ +, π +, K +, p at 5, 10 and 13 GeV/ c. Data on the energy and coordinate resolution, hadron and electromagnetic shower separation have been obtained.

HighP ? hadron production off nuclei at 70 GeV

Invariant cross sections for hadron production (π±,K ± ,p and\(\bar p\)) by protons off C, Al, Cu, Sn and Pb nuclei have been measured at 70 GeV for theP∧ range from 1 up to 4.65 GeV/c. TheA-dependence of the invariant cross section is not described by the exponentialAα(P∧), which points to the presence of secondary hadron absorption in nuclei.