Asymptotic power laws for hadron calorimeter experiments

This is a study of asymptotic QCD predictions for collisions in which a finite fraction of the available energy is carried by hadrons into an angular region $\text{Ω}$ whose complement is $\text{Ω}{}_{\mathrm{<mtext>a</mtext>}}$ or $\text{Ω}{}_{\mathrm{<mtext>b</mtext>}}$ or $\text{Ω}{}_{\mathrm{<mtext>a</mtext>}}\text{UΩ}{}_{\mathrm{<mtext>b</mtext>}}\text{, Ω}{}_{\mathrm{<mtext>a</mtext>}}$ being fixed cones about the directions of motion of the initial particles. Apart from slow (logarithmic) corrections the asymptotic power laws derived from the covariant parton model appear to be justified provided certain conditions on $\text{Ω}{}_{\mathrm{<mtext>a</mtext>}}$ and/or $\text{Ω}{}_{\mathrm{<mtext>b</mtext>}}$ and the energy deposited in them are met.     

Production of hadron resonances in heavy-ion collisions

The role of microscopic kinetics in the production of short-lived (broad) hadron resonances from subhadronic nuclear matter is considered. Anew approach to calculating the multiplicity of broad meson resonances is proposed. This approach takes explicitly into account the possibility that massive constituent quarks play a decisive role at the last stage of the expansion and cooling of matter produced in the central collisions of relativistic heavy nuclei. The resulting theoretical estimates are comparedwith available experimental data, and some quantitative and qualitative predictions are made.     

Direct hadron production in ultrarelativistic heavy-ion collisions

Hadrons emitted by the pre-surface layer of a quark-gluon plasma (QGP) before the phase transition into a hadronic gas are considered as possible sources of direct information about QGP. It is shown that if QGP is created in ultrarelativistic heavy-ion collisions, then these hadrons strongly contribute at soft p_t at SpS energy and dominate up to an order of magnitude at LHC energy.     

Simulations for CMS hadron endcap calorimeter upgrade at HL-LHC

The upgrade of the present endcap calorimeters is foreseen to prepare the CMS experiment for the High Luminosity LHC. Integrated doses at the location of the front layers of the hadron endcap calorimeter are expected to reach 20 Mrad. Studies of radiation fields are presented in this report. At the same time, the effects of pileup will become more severe, making the identification of jet objects more challenging. We estimated the effects of different transverse segmentations of back hadron calorimeter (BH) for CMS upgrade.     

Forward gluon production in hadron–hadron scattering with pomeron loops

We discuss new physical phenomena expected in particle production in hadron–hadron collisions at high energy, as a consequence of pomeron loop effects in the evolution equations for the color glass condensate. We focus on gluon production in asymmetric, ‘dilute–dense’, collisions: a dilute projectile scatters off a dense hadronic target, whose gluon distribution is highly evolved. This situation is representative for particle production in proton–proton collisions at forward rapidities (say, at LHC) and admits a dipole factorization similar to that of deep inelastic scattering (DIS). We show that at sufficiently large forward rapidities, where the pomeron loop effects become important in the evolution of the target wavefunction, gluon production is dominated by ‘black spots’ (saturated gluon configurations) up to very large values of the transverse momentum, well above the average saturation momentum in the target. In this regime, the produced gluon spectrum exhibits diffusive scaling, so like DIS at sufficiently high energy.     

Similarity of hadron production inpp and heavy-ion collisions

The characteristic features of pseudorapidity distributions of hadron production are investigated in terms of a geometrical parameterh≡(dn/dη)₀/Φ, Φ being the phase space covered by the η distribution. It is found thath is about the same for the heavy-ion (HI) andpp collisions at the same energy, the same for π andK production and behaves ash～E _cm ^?1/3 . This similarity property yieldsK ^?/π^?=0.041±0.004 andK ⁺/K ^?=4.5±0.6 for HI collisions at 14.6 GeV/A in agreement with BNL experiments.     

Search for anomalous and exotic cosmic rays phenomena in the CMS experiment on the CASTOR calorimeter at the large hadron collider

The creation of the CASTOR forward calorimeter in the compact muon spectrometer (CMS) experiment at the Large Hadron Collider (LHC), CERN enabled us to perform experiments at energies corresponding to those of cosmic rays but at much greater intensities, the most important factor in studying rare and anomalous phenomena.     

Re-hardening of hadron transverse mass spectra in relativistic heavy-ion collisions

We analyze the spectra of pions and protons in heavy-ion collisions at relativistic energies from 2 A GeV to 65+65 A GeV by using a jet-implemented hadron-string cascade model. In this energy region, hadron transverse mass spectra first show softening until SPS energies, and re-hardening may emerge at RHIC energies. Since hadronic matter is expected to show only softening at higher energy densities, this re-hardening of spectra can be interpreted as a good signature of the quark-gluon plasma formation     

Scaling of hadron masses and widths in thermal models for ultrarelativistic heavy-ion collisions

By means of a simple rescaling, modifications of hadron masses and widths are incorporated into the thermal analysis of particle ratios in ultrarelativistic heavy-ion collisions. We find that moderate, up to 20%, changes of hadron masses do not spoil the quality of the fits, which remain as good as those obtained without modifications. Larger changes are not likely. The fits with the modified masses yield modified values of the optimal temperature and baryon chemical potential. In particular, with decreasing masses of all hadrons (except for pseudo-Goldstone bosons) the fitted values of the temperature and the baryon chemical potential are lowered, with the change approximately proportional to the scaling of masses. In addition, we find that the broadening of the hadron widths by less than a factor of two practically does not affect the fits.     

Electromagnetic and hadron signatures of quark-gluon plasma in heavy-ion collisions at 62.4 GeV in the PHOENIX experiment on the RHIC

The motivation for quark-gluon plasma studies at beam energies of 20–100 GeV are the detailed exploration of the phase diagram of QCD matter and the search for the critical point of deconfinement transition. The PHOENIX experiment on the RHIC measures nuclear modification factors for protons, π⁰ and φ mesons in heavy-ion collisions at $\sqrt s$ 6 = 2.4 GeV. The possibility of obtaining the electromagnetic signatures of quark-gluon plasma measurements with an innovative HBD detector is discussed.     

A method for the separation and reconstructions of charged hadron and neutral hadron from their overlapped showers in an electromagnetic calorimeter

The separation and reconstructions of charged hadron and neutral hadron from their overlapped showers in an electromagnetic calorimeter is very important for the reconstructions of some particles with hadronic decays, for example the tau reconstruction in the searches for the Standard Model and supersymmetric Higgs bosons at the LHC. In this paper, a method combining the shower cluster in an electromagnetic calorimeter and the parametric formula for hadron showers, was developed to separate the overlapped showers between charged hadron and neutral hadron. Taking the hadronic decay containing one charged pion and one neutral pion in the final status of tau for example, satisfied results of the separation of the overlapped showers, the reconstructions of the energy and positions of the hadrons were obtained. An improved result for the tau reconstruction with this decay model can be also achieved after the application of the proposed method.     

The use of Higgs boson production process for optimization of hadron calorimeter segmentation

A new approach to the determination of the optimum transverse segmentation of the hadron calorimeter using the Higgs boson production process via the vector boson fusion mechanism is considered. Monte Carlo simulation results are presented for the hadron calorimeter which will be installed after the modernization of 2023 in the Compact Muon Superdetector collaboration at the Large Hadron Collider of the CERN.     

On the projectile fragmentation in heavy-ion reactions at intermediate energies

The two-body fragmentation of the projectile in the target field is described within a three-body dynamic model. Four types of reaction emerge: fusion at low energies and low impact parameters b, elastic and inelastic reactions at high b and two types of fragmentation in peripheral collisions. For high b the two projectile parts are emitted while for low b one fragment fuses with the target and only the other one can be detected. In the first case the part which has grazed the target has been strongly slackened and has a velocity of 0.7 V beam for small emission angles to 0.5 V beam for large angles. It might be a contribution to the relaxed fragment events detected at intermediate angles. In agreement with experimental data, the b² window for this kind of fragmentation is very narrow for heavy quasi-projectiles and widens with decreasing masses. This model allows to reproduce semi-quantitatively the mass distribution of the quasi-projectiles, the position of the maximum in the one- and two-peak energy spectra and the relative importance of the two types of fragmentation.     

Scaling of hadron production bypp,p-nucleus and heavy-ion collisions

The rest-frame of secondaries frompp collisions determined by the covariant Boltzmann factor is found to be independent of the massm of the secondary. In this frame, the hadron production behaves like bremsstrahlung:n(m)～W ^* (m)/m ²,W ^* (m) being the available energy. This multiplicity law fitsp+p→m+? at 400 GeV/c of NA 27 Collaboration without free-parameters. Extended top-nucleus and heavy-ion collisions, assuming a mean-free-path of collision between the incident and the target nucleon to be ～2.80 fm and 1.63 fm respectively, it accounts forn(K ^?) and \(n(\bar \Lambda )\) of CERN-SPS experiments and theK ^?/π^? ratio of BNL experiments.     

Nuclear-nuclear collision centrality determination by the spectators calorimeter for the MPD setup at the NICA facility

The work conditions of the hadron calorimeter for spectators registration (Zero Degree Calorimeter, ZDC) were studied for the heavy nuclei collisions with the several GeV invariant energy. The ZDC simulations were performed for the MPD (Multi-Purpose Detector) at the NICA (Nuclotron-based Ion Collider fAcility) collider, which are under developement at the Joint Institute for Nuclear Research (JINR, Dubna). Taking into account the spectator nuclear fragments leads to a nonmonotonic dependence of the ZDC response on the impact parameter. The reason for this dependence studied with several event generators is the primary beam hole in the ZDC center. It is shown, that the ZDC signal should be combined with a data from other MPD@NICA detector subsystems to determine centrality.     

On-line isotope separation of projectile fragments produced in relativistic heavy-ion reactions

A new on-line isotope separator was constructed and used successfully for the study on short-lived isotopes at the Bevalac at Lawrence Berkeley Laboratory. The isotopes were produced through projectile fragmentation processes of high energy heavy-ion reactions. Various isotopes were rigidity-separated by use of a beam line and, finally, the desired single isotope was range analyzed to stop in a catcher. A large number of β-emitting²¹F nuclei were successfully collected and the nuclear lifetime was determined by detecting β-rays.     

Polarization in projectile fragmentation andg-factor measurements for neutron-rich nuclei

A method to produce beams of polarized unstable nuclei was developed, which fully exploits the advantageous features of the projectile fragmentation reaction. The method was applied tog-factor measurements of several neutron-rich nuclei. We present experimental results so far obtained and discuss capabilities and limitations the present polarization method has.