Publications

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First measurement of the forward rapidity gap distribution in pPb collisions at 8 TeV

Dmitry E. Sosnov

SciPost Phys. Proc. 8, 065 (2022) · published 12 July 2022 | · pdf

We present the forward rapidity gap spectra from proton-lead collisions for both I\!P-Pb and I\!P-p topologies measured at the CMS at a center-of-mass energy of 8.16 TeV. For the I\!P-Pb topology, the cross-section predicted by EPOS-LHC is a factor of two lower than the data while has reasonable description of the spectrum shape. For the I\!P-p topology, the EPOS-LHC, QGSJET~II and HIJING predictions are significantly lower than the data, what can be explained by a contribution of ultra-peripheral photoproduction events. The obtained data may be of significant input for understanding the high energy limit of QCD and modeling cosmic ray air showers.
$tW$ and $tZ'$ production at hadron colliders

Nikolaos Kidonakis, Marco Guzzi, Nodoka Yamanaka

SciPost Phys. Proc. 8, 064 (2022) · published 12 July 2022 | · pdf

We present theoretical results with soft-gluon corrections for two separate processes: (1) the production of a single top quark in association with a $W$ boson in the Standard Model; and (2) the production of a single top quark in association with a heavy $Z'$ boson in new physics models with or without anomalous couplings. We show that the higher-order corrections from soft-gluon emission are dominant for a wide range of collider energies. Results are shown for the total cross sections and top-quark transverse-momentum and rapidity distributions for $tW$ and $tZ'$ production at LHC and future collider energies up to 100 TeV. The uncertainties from scale dependence and parton distribution functions are also analyzed.
Nucleon and pion PDFs: large-x asymptotics meets functional mimicry

Aurore Courtoy, Pavel M. Nadolsky

SciPost Phys. Proc. 8, 063 (2022) · published 12 July 2022 | · pdf

We review strategies to unveil the primordial large-$x$ structure of the nucleons as well as the pion from hard-scattering experiments. Ideas are presented for learning about the $x\to 1$ limit of nonperturbative QCD dynamics at energy scales of order 1 GeV from collider experiments at much higher scales. The behavior of parton distributions at $x\to 1$ predicted by the quark counting rules and other low-energy theoretical approaches is contrasted with phenomenological PDFs. Polynomial mimicry of PDF parametrizations is one of many factors that influence the apparent power of the $(1-x)$ falloff. We discuss implications of the mimicry for the large-$x$ falloff of the pion PDFs.
Proton reconstruction with the Precision Proton Spectrometer (PPS) in Run 2 and the PPS at HL-LHC

Fabrizio Ferro

SciPost Phys. Proc. 8, 062 (2022) · published 12 July 2022 | · pdf

The Precision Proton Spectrometer (PPS) started operating in 2016 and has collected more than 110 fb$^{-1}$ of data over the course of the LHC Run 2, now fully available for physics analysis. This contribution covers the key features of the PPS alignment and optics calibration, which have been developed from scratch. The reconstructed proton distributions, the performance of the PPS simulation and finally the validation of the full reconstruction chain with physics data (dilepton events) are also illustrated.
Prospects of a future multi-TeV muon collider

M. Casarsa

SciPost Phys. Proc. 8, 061 (2022) · published 12 July 2022 | · pdf

A multi-TeV muon collider is a discovery machine and an invaluable tool for many new standard model precision measurements such as the shape of the Higgs boson potential. The update of the European Strategy for Particle Physics recognized the unique opportunity of a muon collider to reach the energy frontier, despite the challenges to produce intense collimated muon beams. The options of a collider at 3 TeV and a collider at 10 TeV or above are the main focus of the forming International Muon Collider Collaboration as well as of the discussion panels at the ongoing US Snowmass process.
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 | · 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 | · 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 | · 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 | · 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 | · 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

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