Two-Particle Correlations in Heavy-Light Ion Collisions

We study the initial, high-energy scatterings in heavy ion collisions using the saturation/Color Glass Condensate framework. We focus on two-particle long-range rapidity correlations which are modeled as two-gluon correlations. We calculate the two-gluon production cross section using the saturation framework in the heavy-light ion regime, including all-order saturation effects in the heavy nucleus while considering only two-orders in the light ion. The two-gluon production cross section generates four types of long-range in rapidity correlations: (i) geometric correlations, (ii) Hanbury Brown and Twiss (HBT) like correlations accompanied by a back-to-back maximum, (iii) near-side correlations, and (iv) away-side azimuthal correlations. The geometric correlations (i) are due to the fact that nucleons are correlated by simply being confined within the same nucleus. Correlations (iii) and (iv) have exactly the same amplitudes along with azimuthal and rapidity shapes: one centered around $\Delta \phi =0$ and the other one centered around $\Delta \phi =\pi$ (here $\Delta \phi$ is the azimuthal angle between the two produced gluons). The geometry dependence of the correlation function leads to stronger azimuthal near- and away-side correlations in the tip-on-tip U+U collisions than in the side-on-side U+U collisions, an exactly opposite behavior from the correlations generated by the elliptic flow of the quark-gluon plasma: a study of azimuthal correlations in the U+U collisions may help to disentangle the two sources of correlations. Finally we rewrite our result for the two-gluon production cross-section in a $k_T$-factorized form resulting in an expression involving a convolution of one- and two-gluon Wigner distributions over the transverse momenta and impact parameters. This differs from the $k_T$-factorized forms used in the literature.Comment: 161 pages, 38 figures, Ph.D. dissertatio

Regularization of the Light-Cone Gauge Gluon Propagator Singularities Using Sub-Gauge Conditions

Perturbative QCD calculations in the light-cone gauge have long suffered from the ambiguity associated with the regularization of the poles in the gluon propagator. In this work we study sub-gauge conditions within the light-cone gauge corresponding to several known ways of regulating the gluon propagator. Using the functional integral calculation of the gluon propagator, we rederive the known sub-gauge conditions for the theta-function gauges and identify the sub-gauge condition for the principal value (PV) regularization of the gluon propagator's light-cone poles. The obtained sub-gauge condition for the PV case is further verified by a sample calculation of the classical Yang-Mills field of two collinear ultrarelativistic point color charges. Our method does not allow one to construct a sub-gauge condition corresponding to the well-known Mandelstam-Leibbrandt prescription for regulating the gluon propagator poles.Comment: 19 pages, 2 figure

Classical Gluon Production Amplitude for Nucleus-Nucleus Collisions: First Saturation Correction in the Projectile

We calculate the classical single-gluon production amplitude in nucleus-nucleus collisions including the first saturation correction in one of the nuclei (the projectile) while keeping multiple-rescattering (saturation) corrections to all orders in the other nucleus (the target). In our approximation only two nucleons interact in the projectile nucleus: the single-gluon production amplitude we calculate is order-g^3 and is leading-order in the atomic number of the projectile, while resumming all order-one saturation corrections in the target nucleus. Our result is the first step towards obtaining an analytic expression for the first projectile saturation correction to the gluon production cross section in nucleus-nucleus collisions.Comment: 37 pages, 24 figure

Pressure Broadening and Shift of the Cesium D\u3csub\u3e1\u3c/sub\u3e Transition by the Noble Gases and N\u3csub\u3e2\u3c/sub\u3e, H\u3csub\u3e2\u3c/sub\u3e, HD, D\u3csub\u3e2\u3c/sub\u3e, CH\u3csub\u3e4\u3c/sub\u3e, C\u3csub\u3e2\u3c/sub\u3eH\u3csub\u3e6\u3c/sub\u3e, CF\u3csub\u3e4\u3c/sub\u3e, and \u3csup\u3e3\u3c/sup\u3eHe

The pressure broadening and shift rates for the cesium D1 (62P1/2 ← 6 2S1/2) transition with the noble gases and N2, H2, HD, D2, CH4, C2H6, CF4, and 3He were obtained for pressures less than 300 torr at temperatures under 65 °C by means of laser absorption spectroscopy. The collisional broadening rate, γL, for He, Ne, Ar, Kr, Xe, N2, H2, HD, D2, CH4, C2H6, CF4, and 3He are 24.13, 10.85, 18.31, 17.82, 19.74, 16.64, 20.81, 20.06, 18.04, 29.00, 26.70, 18.84, and 26.00 MHz/torr, respectively. The corresponding pressure-induced shift rates, δ, are 4.24, −1.60, −6.47, −5.46, −6.43, −7.76, 1.11, 0.47, 0.00, −9.28, −8.54, −6.06, and 6.01 MHz/torr. These rates have then been utilized to calculate Lennard-Jones potential coefficients to quantify the interatomic potential surfaces. The broadening cross section has also been shown to correlate with the polarizability of the collision partner

Correlations and the ridge in the Color Glass Condensate beyond the glasma graph approximation

We consider two-gluon production in dilute-dense collisions within the Color Glass Condensate framework, applicable to both proton-nucleus and heavy-light ion collisions. We go beyond the glasma graph approximation which is valid in the dilute-dilute limit and show the correspondence between the glasma graphs and the kT-factorized approach that we use in our calculation. We then identify the classical uncorrelated, and the Hanbury-Brown-Twiss (HBT) and Bose enhancement correlated contributions, with the Bose enhancement contribution being suppressed by the number of degrees of freedom with respect to the uncorrelated piece. We show that both the HBT and the Bose enhancement pieces survive the inclusion of higher order contributions in density and that they stem from the quadrupole piece of the two-gluon inclusive cross section. Finally, we illustrate the results using a toy model that allows a simple numerical implementation.The work of TA is supported by Grant No. 2017/26/M/ST2/01074 of the National Science Centre, Poland. The work of NA and DEW were supported by the European Research Council grant HotLHC ERC-2011-StG-279579, Ministerio de Ciencia e Innovaci on of Spain under project FPA2014-58293-C2-1-P and Unidad de Excelencia Mar a de Maetzu under project MDM-2016-0692, Xunta de Galicia (Conseller a de Educaci on) within the Strategic Unit AGRUP2015/11, and FEDER. This work has been performed in the framework of COST Action CA15213 \Theory of hot matter and relativistic heavy-ion collisions" (THOR).S

Multiparticle production at mid-rapidity in the color-glass condensate

In this paper, we compute a number of cross sections for the production of multiple particles at mid-rapidity in the semi-dilute / dense regime of the color-glass condensate (CGC) effective field theory. In particular, we present new results for the production of two quark-antiquark pairs (whether the same or different flavors) and for the production of one quark-antiquark pair and a gluon. We also demonstrate the existence of a simple mapping which transforms the cross section to produce a quark-antiquark pair into the corresponding cross section to produce a gluon, which we use to obtain various results and to cross-check them against the literature. We also discuss hadronization effects in the heavy flavor sector, writing explicit expressions for the production of various combinations of D and D¯ mesons, J/ψ mesons, and light hadrons. The various multiparticle cross sections presented here contain a wealth of information and can be used to study heavy flavor production, charge-dependent correlations, and “collective” flow phenomena arising from initial-state dynamics.This work is supported in part by the U.S. Department of Energy grant DE-FG02-03ER41260 and the BEST (Beam Energy Scan Theory) DOE Topical Collaboration (MM), DOE Contract No. DE-AC52- 06NA25396 and the DOE Early Career Program (MS), the European Research Council 39 grant HotLHC ERC-2011-StG-279579, Ministerio de Ciencia e Innovaci on of Spain under project FPA2014-58293-C2-1-P and Unidad de Excelencia María de Maeztu under project MDM-2016-0692, Xunta de Galicia (Conseller a de Educaci on) and FEDER (DW)S