On jet structure in heavy ion collisions Lokhtin, I. P.; Alkin, A. A.; Snigirev, A. M.
The European physical journal. C, Particles and fields,
09/2015, Letnik:
75, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The LHC data on jet fragmentation function and jet shapes in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed and interpreted in the frameworks of PYthia QUENched ...(PYQUEN) jet quenching model. A specific modification of longitudinal and radial jet profiles in most central PbPb collisions as compared with pp data is close to that obtained with PYQUEN simulations, taking into account wide-angle radiative and collisional partonic energy losses. The contribution of radiative and collisional loss to the medium-modified intra-jet structure is estimated.
An analysis of the data on forward
and
scattering is performed making use of the single- and double-subtraction integral and comparing with derivative dispersion relations for amplitudes. Various ...pomeron and odderon models for the total cross sections are considered and compared. The real part of the amplitude is calculated via dispersion relations. It is shown that the integral dispersion relations lead to a better description of the data for
. Predictions of the considered models for the TOTEM experiment at LHC energies are given.
Special enzymes are necessary for producing gluten-free foods, and specific proteolytic enzymes with gluten-degrading activity may be used as oral treatments for celiac disease. Enzymes of the kind ...were sought, identified, and preliminarily characterized in two strains of the alkaliphilic microscopic fungi
Sodiomyces alkalinus
and
S. magadiensis.
Post-glutamine cleaving activity was for the first time observed in the strains along with proline-cleaving activities of dipeptidyl peptidase 4 (DPP4) and proline aminopeptidase (PAP), allowing efficient hydrolysis of both proline/glutamine-rich gluten peptides and whole gluten. The optimal pH and pH-dependent stability were determined for the peptidases in question. All of the enzymes shown to cleave the prolyne/glutamine-containing bonds were assigned to the serine peptidase group and were found to be stable in moderately acidic and alkaline conditions. Owing to their activities, the peptidases are promising as tools to produce gluten-free foods and to design diets for gluten-intolerant patients.
We discuss the profile of the impact-parameter dependent elastic scattering amplitude. Extraction of impact-parameter dependence from the data set with inclusion of the experimental data on elastic ...scattering at the LHC energies helps to reveal the asymptotics of hadron interactions. Analysis of the data clearly indicates that the impact-parameter elastic scattering amplitude exceed the black disk limit at the LHC energy 7 TeV and the inelastic overlap function reaches its maximum value at b > 0.
The measurement of the production of charm jets, identified by the presence of a D$^{0}$ meson in the jet constituents, is presented in proton–proton collisions at centre-of-mass energies of $ ...\sqrt{s} $ = 5.02 and 13 TeV with the ALICE detector at the CERN LHC. The D$^{0}$ mesons were reconstructed from their hadronic decay D$^{0}$ → K$^{−}$π$^{+}$ and the respective charge conjugate. Jets were reconstructed from D$^{0}$-meson candidates and charged particles using the anti-k$_{T}$ algorithm, in the jet transverse momentum range 5 < p$_{T,chjet}$< 50 GeV/c, pseudorapidity |η$_{jet}$| < 0.9 − R, and with the jet resolution parameters R = 0.2, 0.4, 0.6. The distribution of the jet momentum fraction carried by a D$^{0}$ meson along the jet axis $ \left({z}_{\Big\Vert}^{\textrm{ch}}\right) $ was measured in the range 0.4 <$ {z}_{\Big\Vert}^{\textrm{ch}} $< 1.0 in four ranges of the jet transverse momentum. Comparisons of results for different collision energies and jet resolution parameters are also presented. The measurements are compared to predictions from Monte Carlo event generators based on leading-order and next-to-leading-order perturbative quantum chromodynamics calculations. A generally good description of the main features of the data is obtained in spite of a few discrepancies at low p$_{T,chjet}$. Measurements were also done for R = 0.3 at $ \sqrt{s} $ = 5.02 and are shown along with their comparisons to theoretical predictions in an appendix to this paper.graphic not available: see fulltext
The first measurement of the production of pions, kaons, (anti-)protons and ϕ mesons at midrapidity in Xe–Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV is presented. Transverse momentum ...(pT) spectra and pT-integrated yields are extracted in several centrality intervals bridging from p–Pb to mid-central Pb–Pb collisions in terms of final-state multiplicity. The study of Xe–Xe and Pb–Pb collisions allows systems at similar charged-particle multiplicities but with different initial geometrical eccentricities to be investigated. A detailed comparison of the spectral shapes in the two systems reveals an opposite behaviour for radial and elliptic flow. In particular, this study shows that the radial flow does not depend on the colliding system when compared at similar charged-particle multiplicity. In terms of hadron chemistry, the previously observed smooth evolution of particle ratios with multiplicity from small to large collision systems is also found to hold in Xe–Xe. In addition, our results confirm that two remarkable features of particle production at LHC energies are also valid in the collision of medium-sized nuclei: the lower proton-to-pion ratio with respect to the thermal model expectations and the increase of the ϕ-to-pion ratio with increasing final-state multiplicity.
HYDJET++ model combines the description of soft processes with the treatment of hard partons propagating hot and dense nuclear medium. The model is employed for the analysis of PbPb collisions at LHC ...energies. The cross-talk of elliptic v2 and triangular v3 flow in the model generates both even and odd harmonics of higher order, as well as long-range azimuthal dihadron correlations (“ridge” structure). The simple modification of the model via introducing the distribution over spatial anisotropy parameters permits HYDJET++ to reproduce both v2 and v3 flow fluctuations and related to it eccentricity fluctuations of the initial state. The data on momentum spectra and elliptic flow of charmed mesons are reproduced by HYDJET++ including thermal and non-thermal charm production mechanisms. A tolerable agreement of HYDJET++ predictions with the data for hard probes (including such observables as high-pT hadron and jet nuclear modification factors, and specific modification of longitudinal and radial jet profiles) testifies in favour of successful treatment of the hard component based on PYQUEN event generator.
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