Publications

Order by: publication date number of citations

• Non-zero transverse single spin asymmetry of very forward $\pi^0$ in polarized $p + p$ collisions at $\sqrt{s} = 510$ GeV

  Minho H. Kim

  SciPost Phys. Proc. 8, 060 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The RHICf experiment measured transverse single spin asymmetry of very forward ($\eta > 6$) $\pi^0$ from polarized $p + p$ collisions at $\sqrt{s} = 510$ GeV. In order to measure it precisely, we installed a new electromagnetic calorimeter at zero-degree area of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) and measured the $\pi^0$s over the kinematic range of $x_F > 0.25$ and $0 < p_T < 1$ GeV/$c$ in June, 2017. A clear non-zero asymmetry was observed even in low $p_T < 1$ GeV$c$ showing a similar $x_F$ dependence with the forward ($2 < \eta < 4$) $\pi^0$ ones. A possible diffractive contribution may need to be taken into account to explain the very forward $\pi^0$ asymmetry. RHICf-STAR combined analysis and follow-up experiment will give a clue to understand it qualitatively.

• Measurement of splittings along a jet shower in $\sqrt{s} = 200$ GeV pp collisions at STAR

  Raghav Kunnawalkam Elayavalli

  SciPost Phys. Proc. 8, 059 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Jets are algorithmic proxies of hard scattered partons, i.e. quarks and gluons, in high energy particle collisions. The STAR collaboration presents the first measurements of substructure observables at the first, second and third splits in the jet clustering tree via the iterative SoftDrop procedure. For each of these splits, we measure the fully corrected groomed shared momentum fraction (\zg) and groomed jet radius (\rg). We discuss the evolution of jet substructure in both the angular and momentum scales which allows for a self-similarity test of the DGLAP splitting function. We compare the fully corrected data to Monte Carlo models, providing stringent constraints on model parameters related to the parton shower and non-perturbative effects such as hadronization.

• Impact parameter dependence of color charge correlations in the proton

  Adrian Dumitru, Heikki Mäntysaari, Risto Paatelainen

  SciPost Phys. Proc. 8, 058 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The impact parameter dependence of color charge correlators in the proton is obtained from the light front formalism in light cone gauge. We include NLO corrections due to the $|qqqg\rangle$ Fock state via light-cone perturbation theory. Near the center of the proton, the $b$-dependence of the correlations is very different from a "transverse profile function". The resulting $t$-dependence of exclusive $J/\Psi$ photoproduction transitions from exponential to power law at $|t| \approx 1$ GeV$^2$. This prediction could be tested at upcoming DIS facilities or in nucleus-proton ultraperipheral collisions (UPCs).

  2 citations

• Twist-3 partonic distributions from lattice QCD

  Shohini Bhattacharya, Krzysztof Cichy, Martha Constantinou, Andreas Metz, Aurora Scapellato, Fernanda Steffens

  SciPost Phys. Proc. 8, 057 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Twist-3 partonic distributions contain important information that characterizes nucleon's structure. In this work, we show our lattice exploration of the twist-3 PDFs $g_T(x)$, and $h_L(x)$. We also present our preliminary results on the twist-3 GPD $\tilde{G}_2(x)$. We use the quasi-distribution approach to connect the lattice-extracted matrix elements, renormalized in the RI/MOM scheme, to light-cone distributions, applying the matching procedure that we developed in parallel. We also calculate the twist-2 counterparts of $g_T(x)$ and $h_L(x)$, i.e. $g_1(x)$, and $h_1(x)$, and test the Wandzura-Wilczek approximation.

  2 citations

• Zero modes and matching for the twist-3 PDFs

  Shohini Bhattacharya, Krzysztof Cichy, Martha Constantinou, Andreas Metz, Aurora Scapellato, Fernanda Steffens

  SciPost Phys. Proc. 8, 056 (2022) · published 12 July 2022 | Toggle abstract · pdf

  The quasi-PDF approach, proposed by X. Ji in 2013, has made it possible to directly extract light-cone PDFs from lattice QCD. This approach relies on the extraction of matrix elements of space-like operators for fast-moving hadrons. Quasi-PDFs can be related to the light-cone PDFs through a perturbatively calculable matching coefficient. We explore the formalism of matching, for the very first time, for the twist-3 PDFs $g_{T}(x)$, $e(x)$ and $h_{L}(x)$. In this work, we address the non-trivialities involved in the extraction of the matching coefficient due to the presence of (singular) zero-mode contributions.

  1 citation

• Open strange meson $K^\pm_1$ in hot and dense nuclear matter

  Rajesh Kumar, Arvind Kumar

  SciPost Phys. Proc. 8, 055 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Using the unification of the chiral SU(3) model and QCD sum rules, we deduce the in-medium properties of $K^\pm_1$ meson. Within the chiral SU(3) model, medium modified gluon and quark condensates are evaluated through their interactions with the scalar fields ($\sigma$, $\zeta$, $\delta$, and $\chi$). These condensates are further used as input in the Borel transformed equations of QCD sum rules to evaluate the in-medium mass of strange $K^\pm_1$ meson. The in-medium property of the above meson can be used to study the restoration of chiral symmetry in nuclear matter.

  1 citation

• Multi-particle production in proton-nucleus collisions in the Color Glass Condensate

  Pedro Augusto Agostini Infante, Tolga Altinoluk, Nestor Armesto

  SciPost Phys. Proc. 8, 054 (2022) · published 12 July 2022 | Toggle abstract · pdf

  We compute multi-gluon production in the Color Glass Condensate approach in dilute-dense collisions, p$A$. We include the contributions that are leading in the overlap area of the collision but keep all orders in the expansion in the number of colors. We use a form of the Lipatov vertices that leads to the Wigner function approach for the projectile previously employed, that we generalise to take into account quantum correlations in the projectile wave function. We compute four gluon correlations and we find that the second order four particle cumulant is negative, so a sensible second Fourier azimuthal coefficient can be defined.

• Investigation of the background in coherent $J/\psi$ production at the EIC

  Wan Chang

  SciPost Phys. Proc. 8, 053 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Understanding fundamental properties of nucleons and nuclei are among the most important scientific goals of the next-generation machine, the Electron-Ion Collider (EIC). With the unprecedented versatility provided by the EIC, it will provide answers to many standing puzzles and open questions in modern nuclear physics. One of the golden measurements at the EIC is coherent vector meson production in electron-nucleus (eA) scattering in order to obtain the spatial gluon density distribution in heavy nuclei. This requires the experiment to overcome an overwhelmingly large background arising from the incoherent diffractive production, where the nucleus mostly breaks up into fragments of particles in the far-forward direction close to the hadron beam rapidity. In this talk, we systematically study the rejection of incoherent $J/\psi$ production by vetoing products from the nuclear breakup - protons, neutrons, and photons, which is modeled with the BeAGLE event generator and the most up-to-date EIC Far-forward Interaction Region design.

• A new method to extract the valence transversity distributions

  Mauro Anselmino, Raj Kishore, Asmita Mukherjee

  SciPost Phys. Proc. 8, 052 (2022) · published 12 July 2022 | Toggle abstract · pdf

  A new method is suggested for the extraction of $u$-quark and $d$-quark transversity distributions, using single spin asymmetry (SSA) data in semi-inclusive deep inelastic scattering (SIDIS) processes, where they couple to the Collins or the di-hadron fragmentation functions. We discuss a recent suggestion to extract the transversity distribution using the concept of difference asymmetries and their ratios, which avoids the requirement of Collins function. We suggest new measurements, involving ratios of polarized cross-sections, that would directly probe the ratio $h_1^{d_v}/h_1^{u_v}$. We also show some numerical estimates.

• Correlations between azimuthal asymmetries and multiplicity and mean transverse momentum in small collisions systems in the CGC

  Tolga Altinoluk, Néstor Armesto, Alex Kovner, Michael Lublinsky, Vladimir V. Skokov

  SciPost Phys. Proc. 8, 051 (2022) · published 12 July 2022 | Toggle abstract · pdf

  Considering a dilute-dense situation suitable for pA collisions, we compute in the Color Glass Condensate the correlation between azimuthal asymmetries, specifically the squared second Fourier coefficient $v_2^2$, and the total multiplicity in the event. We also analyse the correlation between $v_2^2$ and the mean squared transverse momentum of particles in the event. In both cases, we find that the correlations are generally very small, consistent with the observations. We also note an interesting sharp change in the value of $v_2^2$ and its correlations as a function of the width of the transverse momentum bin, related with a change of the dominance of Bose and HBT quantum correlations.