Conveners
Small Systems: (1)
- William Zajc (Columbia University)
Small Systems: (2)
- Victoria Greene (Vanderbilt University (US))
Small Systems: (3)
- Gunther Roland (Massachusetts Inst. of Technology (US))
High-energy jets are produced by the fragmentation of partons (quarks and gluons) that underwent hard scattering in the early stages of a collision. For quite a number of years, jets have been successfully used to probe the properties of the special form of matter, the quark gluon plasma (QGP), formed in high-energy heavy ion collisions. One of the most recognized signatures of the QGP, the...
While the formation of the quark--gluon plasma (QGP) in heavy-ion collisions has been confirmed by characteristic patterns of flow measurements, it remains unclear what is the smallest possible collision system that can generate a similar medium exhibiting partonic collectivity. In this talk, we will present the new preliminary results of anisotropic flow in pp, p--Pb, and Pb--Pb collisions...
The LHCb spectrometer has the unique capability to function as a fixed-
target experiment by injecting gas into the LHC beampipe while proton or ion
beams are circulating. The resulting beam+gas collisions cover an unexplored
energy range, intermediate to previous fixed-target experiments and the top
RHIC energy for AA collisions, and allow systems of different size to be stud-
ied. Here...
The JETSCAPE Collaboration reports new studies of jet transport in the QGP using Bayesian Inference, incorporating both hadron and jet inclusive yield suppression data, and jet substructure data. This analysis extends the previously published JETSCAPE Bayesian determination of $\hat{q}$, which was based solely on inclusive hadron suppression data.
JETSCAPE is a modular framework for...
We will present the final measurement studying the relationship between the production of hard and soft particles through the correlation of Upsilon meson states (including $\Upsilon$(1S), $\Upsilon$(2S), and $\Upsilon$(3S)) with the inclusive-charged particle yields. The analysis is performed using the full-luminosity ATLAS Run-2 13 TeV $pp$ collision data. A description of the technical...
Employing a dynamical initial state model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the rapidity dependence of anisotropic flow in the Relativistic Heavy-Ion Collider (RHIC) small system scan at 200 GeV center of mass energy. We demonstrate that approximately 50% of the pT-differential triangular flow difference between the measurements by the STAR and PHENIX...
Collectivity in small systems is a crucial area of study in high-energy nuclear physics, as it provides valuable insights into initial conditions and pre-equilibrium stages in heavy-ion collisions. The small system collision scan at RHIC, including both symmetric and asymmetric small systems (O+O $>$ $^{3}$He$+$Au $>$ $d$$+$Au $>$ $p$$+$Au $>$ $\gamma+$Au), provides a better understanding of...
One of the main goals in the study of hadronic interactions at LHC energies is the attempt to characterize the mechanisms involved in particle production in different regimes. The charged-particle multiplicity is one of the most interesting observables in these kind of studies. On the one hand, the pseudorapidity dependence of charged-particle production provides information on the partonic...
The study of jet production in small collision systems is essential for testing our understanding of perturbative and non perturbative QCD and cold nuclear matter effects. In addition, studies at high multiplicity in small collision systems exhibit signatures of collectivity, which is still not fully understood within a unified picture across system size. Jet quenching in small systems is not...
We explore consequences of the existence of gluonic hot spots inside the proton for the initial eccentricities in a proton-nucleus collision [1], and the constraints on the parameters describing these hot spots from coherent and incoherent exclusive vector meson production cross sections in deep inelastic scattering [2].
The eccentricities are calculated by calculating correlation functions...
It has been postulated that nonperturbative quantum chromodynamics (QCD) evolution of a single parton in the vacuum can develop long-range collective effects of a multiparton system, reminiscent of those observed in high-energy nuclear interactions from the formation of a quark-gluon plasma. A search for such QCD collective effects is performed by the CMS experiment via correlation...
Heavy meson production in reactions with nuclei is an active new frontier to understand QCD dynamics and the process of hadronization in nuclear matter. Measurements in various colliding systems at RHIC and LHC, including Pb-Pb, Xe-Xe, O-O, p-Pb, and p-O, enable precision tests of the medium-size, temperature, and mass dependencies of the in-medium parton propagation and shower formation. We...
The observation of signs of collectivity in small systems has highlighted the need
for a better understanding of equilibration in small and large collisions systems.
In search of this, the QCD effective kinetic theory formulated by Arnold, Moore
and Yaffe (AMY) [1] has emerged as a promising candidate. In order to fully exploit
the theory also for phenomenology we introduce ALPACA [2], a...
Strangeness enhancement has long been considered a signature of the quark-gluon plasma formation in heavy-ion collisions. Recently, strangeness enhancement has also been observed in small systems at the LHC, but the underlying physics is not yet fully understood. This motivates studies of strange hadron production in small systems at RHIC, where the energy density of system is expected to be...
The study of heavy-flavour mesons and baryons in hadronic collisions provides unique access to the properties of heavy-quark hadronisation in the presence of large partonic densities, where new mechanisms of hadron formation beyond in-vacuum fragmentation can emerge. Performing these measurements in intervals of charged particle multiplicities provides sensitivity to understand whether...
The thermal fluctuations in the QGP medium formed in heavy ion collisions present themselves as event-wise $[p_\mathrm{T}]$ fluctuations in the final state. Recent studies have shown that in ultra-central collisions, fluctuations are sensitive to radial flow, random thermal motion, and nuclear deformation. They can provide constraints on the extent of thermalization of the QGP droplet. Also of...
Among the most iconic results of Run 1 and Run 2 of the LHC is the observation of enhanced production of (multi-)strange to non-strange particles, gradually rising from low-multiplicity to high-multiplicity pp or p-Pb collisions and reaching values close to those measured in peripheral Pb-Pb collisions. More insightful information about the production mechanism could be provided by measuring...
A key open question in the study of multi-particle production in high-energy $pp$ collisions is the relationship between the "ridge" - observed azimuthal correlations between particles in the underlying event that extend over all rapidities and hard or semi-hard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the...
