arXiv subjects

J. Barrette

Publications and source records attributed to J. Barrette.

At least 19 recordsLinked to original sources

arXiv2016

Predictions for $p+$Pb Collisions at $\sqrt{s_{NN}} = 5$ TeV: Comparison with Data

Predictions made in Albacete {\it et al} prior to the LHC $p+$Pb run at $\sqrt{s_{NN}} = 5$ TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication are also shown here.

hep-ph↗

arXiv2013

Open Charm Production in $p + p$ and Pb + Pb collisions at the CERN Large Hadron Collider

Effects of strong longitudinal colour electric fields (SCF), shadowing, and quenching on the open prompt charm mesons (D$^0$, D$^+$, D$^{*+}$, D${_s}{^+}$) production in central Pb + Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV are investigated within the framework of the {\small HIJING/BB v2.0} model. We compute the nuclear modification factor $R_{\rm PbPb}^{\rm D}$, and show that the above nuclear effects constitute important dynamical mechanisms in the description of experimental data. The strength of colour fields (as characterized by the string tension $κ$), partonic energy loss and jet quenching process lead to a suppression factor consistent with recent published data. Predictions for future beauty mesons measurements have been included. Ratios of strange to non-strange prompt charm mesons in central Pb + Pb and minimum bias (MB) $ p + p$ collisions at 2.76 TeV are also discussed. Minimum bias $p + p$ collisions which constitute theoretical baseline in our calculations are studied at the centre of mass energies $\sqrt{s}$ = 2.76 TeV and 7 TeV.

hep-ph↗

arXiv2013

Predictions for $p+$Pb Collisions at sqrt s_NN = 5 TeV

Predictions for charged hadron, identified light hadron, quarkonium, photon, jet and gauge bosons in p+Pb collisions at sqrt s_NN = 5 TeV are compiled and compared. When test run data are available, they are compared to the model predictions.

hep-ph↗

arXiv2012

Predictions for p+Pb at 5.02A TeV to test initial state nuclear shadowing at the Large Hadron Collider

Collinear factorized perturbative quantum chromodynamics (pQCD) model predictions are compared for $p+{\rm Pb}$ at 5.02$A$ TeV to test nuclear shadowing of parton distribution at the Large Hadron Collider (LHC). The pseudorapidity distribution the nuclear modification factor (NMF), $R_{p{\rm Pb}}(y=0,p_T<20\;{\rm GeV}/{\it c}) = dn_{p{\rm Pb}} /(N_{\rm coll}(b)dn_{pp})$ and the pseudorapidity asymmetry $Y_{asym}^{h}(p_T)=R^h_{pPb}(p_T, η<0)/R^h_{pPb}(p_T,η>0)$ are computed using {\small HIJING/BB v2.0 model} and a pQCD improved parton model kTpQCD\_v2.0 which embedded generalized parton distribution functions (PDFs). These results are updated calculations of those presented in Phys. Rev. C {\bf 85}, 024903 (2012).

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arXiv2012

Hyperon/meson ratios in rare high-multiplicity $pp$ collisions at energies available at the Large Hadron Collider, and potential signatures for mini-quark-gluon plasma formation

We use the framework of the HIJING/BB v2.0 model to simulate high-multiplicity (HM) $p+p$ collision events at the Large Hadron Collider (LHC) to study observables sensitive to possible collective phenomena, such as strong longitudinal color fields (SLCF) modeled by an enhanced string tension ($κ$). We focus on the hyperon/meson yield ratios at center-of-mass (c.m.) energy $\sqrt{s}$ = 7 TeV, in the transverse momentum region, $1 < p_T < 4 $ GeV/{\it c}. For minimum bias events these ratios are well described assuming an energy dependence $κ= κ(s)= κ_{0} (s/s_{0})^{0.04} {\rm GeV/fm}$ ($κ_{0}$= 1 GeV/fm), giving a value $κ= 2$ GeV/fm at $\sqrt{s}$ = 7 TeV. We compare minimum bias (MB) events to simulated HM events assuming that $κ(MB)=2$ GeV/fm could grow to an extreme value of $κ(HM)=5$ GeV/fm that saturates the strangeness suppression factor. With this assumption the model predicts a very strong enhancement of (multi)strange baryon/meson ratios in HM events. If observed, such an enhancement could be also interpreted as a possible signature for formation in HM $p+p$ collision events of a deconfined but out of local thermal equilibrium {\em mini quark-gluon plasma} (mQGP).

hep-ph↗

arXiv2012

Predictions for p+Pb at 4.4A TeV to Test Initial State Nuclear Shadowing at energies available at the CERN Large Hadron Collider

Collinear factorized perturbative QCD model predictions are compared for p+Pb at 4.4A TeV to test nuclear shadowing of parton distribution at the Large Hadron Collider (LHC). The nuclear modification factor (NMF), R_{pPb}(y=0,p_T<20 GeV/c) = dn_{p Pb} /(N_{coll}(b)dn_{pp}), is computed with electron-nucleus (e+A) global fit with different nuclear shadow distributions and compared to fixed Q^2 shadow ansatz used in Monte Carlo Heavy Ion Jet Interacting Generator (HIJING) type models. Due to rapid DGLAP reduction of shadowing with increasing Q^2 used in e+A global fit, our results confirm that no significant initial state suppression is expected (R_{pPb} (p_T) = 1 \pm 0.1) in the p_T range 5 to 20 GeV/ c. In contrast, the fixed Q^2 shadowing models assumed in HIJING type models predict in the above p_T range a sizable suppression, R_{pPb} (p_T) = 0.6-0.7 at mid-pseudorapidity that is similar to the color glass condensate (CGC) model predictions. For central (N_{coll} = 12) p+ Pb collisions and at forward pseudorapidity (η= 6) the HIJING type models predict smaller values of nuclear modification factors (R_{pPb}(p_T)) than in minimum bias events at mid-pseudorapidity (η= 0). Observation of R_{pPb}(p_T= 5-20 GeV/c) less than 0.6 for minimum bias p+A collisions would pose a serious difficulty for separating initial from final state interactions in Pb+Pb collisions at LHC energies.

nucl-th↗

arXiv2011

Baryon anomaly and strong color fields in Pb+Pb collisions at 2.76A TeV at the CERN Large Hadron Collider

With the HIJING/BBbar v2.0 heavy ion event generator, we explore the phenomenological consequences of several high parton density dynamical effects predicted in central Pb+Pb collisions at the Large Hadron Collider (LHC) energies. These include (1) jet quenching due to parton energy loss (dE/dx), (2) strangeness and hyperon enhancement due to strong longitudinal color field (SCF), and (3) enhancement of baryon-to-meson ratios due to baryon-anti-baryon junctions (JJbar) loops and SCF effects. The saturation/minijet cutoff scale p0(s)and effective string tension kappa(s,A) are constrained by our previous analysis of LHC p+p data and recent data on the charged multiplicity for Pb+Pb collisions reported by the ALICE collaboration. We predict the hadron flavor dependence (mesons and baryons) of the nuclear modification factor RAA(pT)$ and emphasize the possibility that the baryon anomaly could persist at the LHC up to pT=10 GeV, well beyond the range observed in central Au+Au collisions at RHIC energies.

hep-ph↗

arXiv2011

Strong longitudinal color field effects in pp collisions at energies available at the Large Hadron Collider

We study the effect of strong longitudinal color fields (SCF) in p+p reactions up to Large Hadron Collider energies in the framework of the HIJING/BBbar v2.0 model that combines (collinear factorized) pQCD multiple minijet production with soft longitudinal string excitation and hadronization. The default vacuum string tension, kappa0 = 1 GeV/fm, is replaced by an effective power law energy dependent string tension, that increases monotonically with center-of-mass energy. The exponent 0.06 is found sufficient to reproduce well the energy dependence of multiparticle observables in RHIC, Tevatron, as well as recent LHC data. This exponent is found to be only half of that predicted by the Color Glass Saturation model, lambda(CGC)=0.115, where gluon fusion multiparticle production mechanisms are assumed. In HIJING/BBbar v2.0, the rapid growth of central-rapidity density with energy is due to the interplay of copious minijet production and increasing SCF contributions. The large (strange)baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of JJbar loops and SCF on baryon-anti-baryon asymmetry and its relation to baryon number transport is also discussed.

hep-ph↗

arXiv2009

Soft Open Charm Production in Heavy-Ion Collisions

Effects of strong longitudinal color electric fields (SCF) on the open charm production in nucleus-nucleus (A + A) collisions at 200A GeV are investigated within the framework of the HIJING-BBbar v2.0 model. A three fold increase of the effective string tension due to in medium effects in A + A collisions, results in a sizeable (60-70 percents) enhancement of the total charm production cross sections. The nuclear modification factors show a suppression at moderate transverse momentum consistent with RHIC data. At Large Hadron Collider energies the model predicts an increase of total charm production cross sections by approximately an order of magnitude.

hep-ph↗

arXiv2007

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.

hep-ph↗

arXiv2007

(Multi)Strangeness Production in Pb+Pb collisions at LHC. HIJING/BBar v2.0 predictions

Strangeness and multi-strangeness particles production can be used to explore the initial transient field fluctuations in heavy ion collisions. We emphasize the role played by Junction anti-Junction (JJbar) loops and strong color electric fields (SCF) in these collisions. Transient field fluctuations of SCF on the baryon production in central (0-5%) Pb+Pb collisions at nucleon-nucleon centre of mass energy of 5.5 TeV will be discussed in the framework of HIJING/BBbar v2.0 model, looking in particular to the predicted evolution of nuclear modification factors R_AA from RHIC to LHC energies. Our results indicate the importance of a good description of the baseline elementary p+p collisions at this energy.

hep-ph↗

arXiv2007

Stopping Power from SPS to LHC energies

We investigate the energy dependence of hadron production and of stopping power based on HIJING/BBbar v2.0 model calculations. Pseudorapidity spectra and transverse momentum distributions for produced charged particles as well as net baryons (per pair of partcipants) and their rapidity loss are compared to data at RHIC and predictions for LHC energies are discussed.

hep-ph↗

arXiv2006

Transient field fluctuations effects in d+Au and Au+Au collisions at \sqrt{s_nn} = 200 GeV

The effect of fluctuations of SCF on the baryon production in d+Au and Au+Au collisions at 200A GeV is studied in the framework of HIJING/BB v2.0 model. An increase of the string tension from kappa_0= 1 GeV/fm, to in medium mean values of 1.5 to 2.0 GeV/fm and 2.0 to 3.0 GeV/fm, for d+Au and Au+Au respectively, results in a consistent description of the observed nuclear modification factors R_dAu and R_AuAu(that relates (d)Au+Au and p+p colllisions) and point to the relevance of fluctuations of transient color fields. The differences between nuclear modification factors R_AuAu and R_CP (that relates central and peripheral collisions) are also discussed. The measurement of multi-strange (anti)hyperons (Ξ, Ω) yields would provide a crucial test of the importance of SCF fluctuations at RHIC energies.

hep-ph↗

arXiv2005

Strong Color Field Baryonic Remnants in Nucleus-Nucleus Collisions at 200A GeV

The effects of strong color electric fields (SCF) on the baryon production at RHIC are studied in the framework of HIJING/BB (v2.0) model. The particle species dependence of nuclear modification factors (NMF) are analyzed for Au+Au collisions at 200A GeV. A doubling of the string tension leading to a modification of the strangeness suppression according to Schwinger mechanism is shown to provide an alternate explanation to coalescence models for the interpretation of the observed baryon and meson production at moderate $p_T$ and results in a predicted enhancement in the (multi)strange (anti)hyperon production.

hep-ph↗

arXiv2004

Baryon Junction Loops in HIJING/BBv2.0 and the Baryon/Meson Anomaly at RHIC

A new version, v2.0, of the HIJING/BB Monte Carlo nuclear collision event generator is introduced in order to explore further the possible role of baryon junctions loops in the baryon/meson anomaly (2 $< p_{T} <$ 5 GeV/c) observed in 200A GeV Au+Au reactions at RHIC. We show that junction loops with an enhanced intrinsic $k_T\approx 1$ GeV/c transverse momentum kick may provide a partial explanation of the anomaly as well as other important baryon stopping observables.

nucl-th↗

arXiv2003

Phase-space density in heavy-ion collisions revisited

We derive the phase space density of bosons from a general boson interferometry formula. We find that the phase space density is connected with the two-particles and the single particle density distribution functions. If the boson density is large, the two particles density distribution function can not be expressed as a product of two single particle density distributions. However, if the boson density is so small that two particles density distribution function can be expressed as a product of two single particle density distributions, then Bertsch's formula is recovered. For a Gaussian model, the effects of multi-particles Bose-Einstein correlations on the mean phase space density are studied.

hep-ph↗

arXiv2003

The Mini-Jet Scale and Energy Loss at RHIC in the HIJING and RQMD Models

The original default mini-jet scale p_0=2 GeV/c and energy loss, dE/dx=2 GeV/fm in HIJING lead to a too rapid growth of the multiplicity with energy. RQMD model without mini-jet leads on the other hand to a too slowly increasing multiplicity with energy. We show that a slight increase of p_0 from the default 2.0 GeV/c at sqrt(s)=130A GeV to 2.2 GeV/c at sqrt{s}=200A GeV is sufficient to account for the bulk observables. Jet quenching of pi^0 above p_T>4 GeV/c at 200A GeV is found to be well reproduced in central Au+Au by the original HIJING default prediction. However, the effective surface emission in the HIJING model formulation of energy loss over-predicts the quenching in more peripheral collisions. Neither HIJING nor HIJING/B{bar}B can account for the observed anomalous excess of moderate p_T<4 GeV/c baryons. The agreement of RQMD with data in this p_T region is shown to be fortuitous because, without mini-jets, it fails to reproduce the p+p spectrum.

nucl-th↗

arXiv2000

Directed flow of antiprotons in Au+Au collisions at AGS

Directed flow of antiprotons is studied in Au+Au collisions at a beam momentum of 11.5A GeV/c. It is shown that antiproton directed flow is anti-correlated to proton flow. The measured transverse momentum dependence of the antiproton flow is compared with predictions of the RQMD event generator.

nucl-ex↗