Publications

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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 | · 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 | · 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 | · 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 | · 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 | · 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 | · 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.
The LHCspin project

M. Santimaria, V. Carassiti, G. Ciullo, P. Di Nezza, P. Lenisa, S. Mariani, L. L. Pappalardo, E. Steffens

SciPost Phys. Proc. 8, 050 (2022) · published 12 July 2022 | · pdf

Broad and unexplored kinematic regions can be accessed at the LHC with fixed-target $pp$, $pA$ and $PbA$ collisions at $\sqrt{s_{\rm{NN}}}=72-115~\rm{GeV}$. The LHCb detector is a fully-instrumented forward spectrometer able to run in fixed-target mode, and currently hosts a target gas cell to take data in the upcoming Run 3. The LHCspin project aims at extending this physics program to Run 4 and to bring polarised physics at the LHC. An overview of the physics potential and a description of the LHCspin experimental setup are presented.

3 citations
Transversity through Dihadron: a constrained fit

Aurore Courtoy

SciPost Phys. Proc. 8, 049 (2022) · published 12 July 2022 | · pdf

We present a study of the valence transversity PDF obtained through a constrained fit. The effects of the constraints on the uncertainties of the PDF are explored. We show that the resulting isovector tensor charge is largely undetermined and, hence, compatible with all lattice evaluations.
Measuring the light meson nuclear modification factor in p-Pb collisions over an unprecedented $p_{\text{T}}$ range with ALICE

Joshua König

SciPost Phys. Proc. 8, 048 (2022) · published 12 July 2022 | · pdf

Differential invariant cross sections of light neutral mesons in p-Pb collisions at $\sqrt{s_{\text{NN}}}$ = 8.16 TeV and in pp collisions at $\sqrt{s}$ = 8 TeV have been measured up to very high transverse momentum ($p_{\text{T}}$). By combining independent reconstruction techniques available in ALICE using the EMCal and PHOS calorimeters as well as the central barrel tracking detectors, the combined spectra cover almost two orders of magnitude in $p_{\rm T}$ for the $\pi^{0}$ meson. The nuclear modification factor $R_{\text{pPb}}$ has been measured for the $\pi^{0}$ and $\eta$ mesons and is found to be consistent with NLO pQCD, CGC and energy loss calculations. Comparisons to the $R_{\text{pPb}}$ of $\pi^{0}$ measured in $\sqrt{s_{\text{NN}}}$ = 5.02 TeV hint at a stronger suppression at low $p_{\rm T}$ with increasing collision energy.
Measurement of Transverse Spin Dependent Azimuthal Correlations of Charged Pion(s) in $p^{\uparrow} p$ Collisions at $\sqrt s = 200$ GeV at STAR

Babu R. Pokhrel

SciPost Phys. Proc. 8, 047 (2022) · published 12 July 2022 | · pdf

At the leading twist, the transversity distribution function, $h^{q}_{1}(x)$, where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the transverse spin structure of the nucleon. Extraction of it is difficult because of its chiral-odd nature. In transversely polarized proton-proton collisions ($p^\uparrow p$), $h_{1}^{q}(x)$ can be coupled with another chiral-odd partner, a spin-dependent fragmentation function (FF). The resulting asymmetries in hadron(s) azimuthal correlations directly probe $h_{1}^{q}(x)$. We report the measurement of correlation asymmetries for charged pion(s) in $p^\uparrow p$, through the Collins and the Interference FF channel.

1 citation

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