Universe

Research

14 pages, 334 KiB

Open AccessArticle

An Update of the Hypothetical X17 Particle

by Attila J. Krasznahorkay, Attila Krasznahorkay, Margit Csatlós, János Timár, Marcell Begala, Attila Krakó, István Rajta, István Vajda and Nándor J. Sas

Universe 2024, 10(11), 409; https://doi.org/10.3390/universe10110409 - 31 Oct 2024

Viewed by 452

Abstract

Recently, when examining the differential internal pair creation coefficients of ⁸Be, ⁴He and ¹²C nuclei, we observed peak-like anomalies in the angular correlation of the e⁺e⁻ pairs. This was interpreted as the creation and immediate decay of [...] Read more.

Recently, when examining the differential internal pair creation coefficients of ⁸Be, ⁴He and ¹²C nuclei, we observed peak-like anomalies in the angular correlation of the e⁺e⁻ pairs. This was interpreted as the creation and immediate decay of an intermediate bosonic particle with a mass of

m_{X} c^{2} \approx

17 MeV, receiving the name X17 in subsequent publications. In this paper, our latest results obtained for the X17 particle are presented by investigating the e⁺e⁻ pair correlations in the decay of the Giant Dipole Resonance (GDR) of ⁸Be. Our results initiated a significant number of new experiments all over the world to detect the X17 particle and determine its properties. In this paper, we will also conduct a mini-review of the experiments whose results are already published, as well as the ones closest to being published. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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13 pages, 478 KiB

Open AccessArticle

Model-Independent Odderon Results Based on New TOTEM Data on Elastic Proton–Proton Collisions at 8 TeV

by Tamás Csörgő, Tamás Novák, Roman Pasechnik, András Ster and István Szanyi

Universe 2024, 10(6), 264; https://doi.org/10.3390/universe10060264 - 17 Jun 2024

Cited by 1 | Viewed by 768

Abstract

Evaluating the

H (x, s | p p)

scaling function of elastic proton–proton (

p p

) collisions from recent TOTEM data at

\sqrt{s} = 8

TeV and comparing it with the same function of elastic proton–antiproton ( [...] Read more.

Evaluating the

H (x, s | p p)

scaling function of elastic proton–proton (

p p

) collisions from recent TOTEM data at

\sqrt{s} = 8

TeV and comparing it with the same function of elastic proton–antiproton (

p \bar{p}

) data of the D0 collaboration at

\sqrt{s} = 1.96

TeV, we find, from this comparison alone, an at least 3.79

σ

signal of odderon exchange. If we combine this model-independently obtained result with that of a similar analysis but using TOTEM elastic

p p

scattering data at

\sqrt{s} = 7

TeV, which resulted in an at least 6.26

σ

signal, the combined significance of odderon exchange increases to at least 7.08

σ

. Further combinations of various datasets in the TeV energy range are detailed in the manuscript. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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18 pages, 980 KiB

Open AccessArticle

Dip-Bump Structure in Proton’s Single Diffractive Dissociation at the Large Hadron Collider

by László Jenkovszky, Rainer Schicker and István Szanyi

Universe 2024, 10(5), 208; https://doi.org/10.3390/universe10050208 - 7 May 2024

Viewed by 915

Abstract

By extending the dipole Pomeron (DP) model, successful in describing elastic nucleon–nucleon scattering, to proton single diffractive dissociation (SD), we predict a dip-bump structure in the squared four-momentum transfer (t) distribution of proton’s SD. Structures in the t distribution of single [...] Read more.

By extending the dipole Pomeron (DP) model, successful in describing elastic nucleon–nucleon scattering, to proton single diffractive dissociation (SD), we predict a dip-bump structure in the squared four-momentum transfer (t) distribution of proton’s SD. Structures in the t distribution of single diffractive dissociation are predicted around

t = - 4

{GeV}^{2}

at LHC energies in the range of 3

{GeV}^{2}

≲ | t | ≲

7

{GeV}^{2}

. Apart from the dependence on s (total energy squared) and t (squared momentum transfer), we predict also a dependence on missing masses. We include the minimum set of Regge trajectories, namely the Pomeron and the Odderon, indispensable at the LHC. Further generalization, e.g., by the inclusion of non-leading Regge trajectories, is straightforward. The present model contains two types of Regge trajectories: those connected with

t

-channel exchanges (the Pomeron, the Odderon, and non-leading (secondary) reggeons) appearing at small and moderate

- t

, where they are real and nearly linear, as well as direct-channel trajectories

α (M^{2})

related to missing masses. In this paper, we concentrate on structures in t neglecting (for the time being) resonances in

M^{2}

. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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11 pages, 637 KiB

Open AccessArticle

Two-Pion Bose–Einstein Correlations in Au+Au Collisions at

\sqrt{s_{N N}}

= 3 GeV in the STAR Experiment

by Anna Kraeva

Universe 2024, 10(4), 188; https://doi.org/10.3390/universe10040188 - 20 Apr 2024

Viewed by 1148

Abstract

The correlation femtoscopy technique makes it possible to estimate the geometric dimensions and lifetime of the particle emission region after the collision of ions. Measurements of the emission region characteristics not only at midrapidity but also at backward (forward) rapidity can provide new [...] Read more.

The correlation femtoscopy technique makes it possible to estimate the geometric dimensions and lifetime of the particle emission region after the collision of ions. Measurements of the emission region characteristics not only at midrapidity but also at backward (forward) rapidity can provide new information about the source and make it possible to impose constraints on the heavy-ion collision models. This work is devoted to revealing the dependence of the spatial and temporal parameters of the emission region of identical pions in Au+Au collisions at

\sqrt{s_{N N}}

= 3 GeV from the fixed-target program of the STAR experiment. The extracted femtoscopic radii,

R_{o u t}

,

R_{s i d e}

,

R_{l o n g}

,

R_{o u t - l o n g}^{2}

, and the correlation strength,

λ

, are presented as a function of collision centrality, pair rapidity, and transverse momentum. Physics implications will be discussed. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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33 pages, 1038 KiB

Open AccessArticle

QED Meson Description of the Anomalous Particles at ∼17 and ∼38 MeV

by Cheuk-Yin Wong

Universe 2024, 10(4), 173; https://doi.org/10.3390/universe10040173 - 7 Apr 2024

Cited by 1 | Viewed by 1459

Abstract

The Schwinger confinement mechanism stipulates that a massless fermion and a massless antifermion are confined as a massive boson when they interact in the Abelian QED interaction in (1+1)D.If we approximate light quarks as massless and apply the Schwinger confinement mechanism to quarks, [...] Read more.

The Schwinger confinement mechanism stipulates that a massless fermion and a massless antifermion are confined as a massive boson when they interact in the Abelian QED interaction in (1+1)D.If we approximate light quarks as massless and apply the Schwinger confinement mechanism to quarks, we can infer that a light quark and a light antiquark interacting in the Abelian QED interaction are confined as a QED meson in (1+1)D. Similarly, a light quark and a light antiquark interacting in the QCD interaction in the quasi-Abelian approximation will be confined as a QCD meson in (1+1)D. The QED and QCD mesons in (1+1)D can represent physical mesons in (3+1)D when the flux tube radius is properly taken into account. Such a theory leads to a reasonable description of the masses of

π^{0}, η

, and

η^{'}

, and its extrapolation to the unknown QED sector yields an isoscalar QED meson at about 17 MeV and an isovector QED meson at about 38 MeV. The observations of the anomalous soft photons, the hypothetical X17 particle, and the hypothetical E38 particle bear promising evidence for the possible existence of the QED mesons. Pending further confirmation, they hold important implications on the properties on the quarks and their interactions. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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11 pages, 826 KiB

Open AccessArticle

Checking the ⁸Be Anomaly with a Two-Arm Electron Positron Pair Spectrometer

by Tran The Anh, Tran Dinh Trong, Attila J. Krasznahorkay, Attila Krasznahorkay, József Molnár, Zoltán Pintye, Nguyen Ai Viet, Nguyen The Nghia, Do Thi Khanh Linh, Bui Thi Hoa, Le Xuan Chung and Nguyen Tuan Anh

Universe 2024, 10(4), 168; https://doi.org/10.3390/universe10040168 - 1 Apr 2024

Cited by 6 | Viewed by 1586

Abstract

We have repeated the experiment performed recently by ATOMKI Laboratory (Debrecen, Hungary), which may indicate a new particle called X17 in the literature. In order to obtain a reliable and independent result, we used a different structure of the electron–positron pair spectrometer at [...] Read more.

We have repeated the experiment performed recently by ATOMKI Laboratory (Debrecen, Hungary), which may indicate a new particle called X17 in the literature. In order to obtain a reliable and independent result, we used a different structure of the electron–positron pair spectrometer at the VNU University of Science. The spectrometer has two arms and simpler acceptance and efficiency as a function of the correlation angle, but the other conditions of the experiment were very similar to the published ones. We could confirm the presence of the anomaly measured at E_p = 1225 keV, which is above the E_p = 1040 keV resonance. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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6 pages, 407 KiB

Open AccessCommunication

Femtoscopy for the NAno-Plasmonic Laser Inertial Fusion Experiments (NAPLIFE) Project

by L. P. Csernai, T. Csörgő, I. Papp, K. Tamosiunas, M. Csete, A. Szenes, D. Vass, T. S. Biró and N. Kroó

Universe 2024, 10(4), 161; https://doi.org/10.3390/universe10040161 - 29 Mar 2024

Viewed by 1236

Abstract

Hanbury-Brown and Twiss analysis is used to determine the size and timespan of emitted particles. Here, we propose to adapt this method for laser-induced nanoplasmonic inertial confinement fusion to determine the parameters of emitted Deuterium and Helium⁴ nuclei. This communication is a [...] Read more.

Hanbury-Brown and Twiss analysis is used to determine the size and timespan of emitted particles. Here, we propose to adapt this method for laser-induced nanoplasmonic inertial confinement fusion to determine the parameters of emitted Deuterium and Helium⁴ nuclei. This communication is a short article that presents part of a larger study over multiple years. It presents a cutting edge method that is new in the field of Inertial Confinement Fusion. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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7 pages, 789 KiB

Open AccessCommunication

Nuclear Modification Factor of Inclusive Charged Particles in Au+Au Collisions at

\sqrt{s_{NN}}

= 27 GeV with the STAR Experiment

by Alisher Aitbayev

Universe 2024, 10(3), 139; https://doi.org/10.3390/universe10030139 - 13 Mar 2024

Viewed by 1296

Abstract

The Beam Energy Scan (BES) program at RHIC aims to explore the QCD phase diagram, including the search for the evidence of the 1st order phase transition from hadronic matter to Quark-Gluon Plasma (QGP) and the location of the QCD critical point. One [...] Read more.

The Beam Energy Scan (BES) program at RHIC aims to explore the QCD phase diagram, including the search for the evidence of the 1st order phase transition from hadronic matter to Quark-Gluon Plasma (QGP) and the location of the QCD critical point. One of the features previously observed in the study of QGP is the effect of suppression of particle production with high transverse momenta

p_{T}

(>2 GeV/c) at energies

\sqrt{s_{N N}}

=

62.4 - 200

GeV, which was deduced from the charged-particle nuclear modification factor (

R_{C P}

) measured using the data from Beam Energy Scan Program Phase I (BES-I) of STAR experiment. In 2018, STAR has collected over 500 million events from

A u

+

A u

collisions at

\sqrt{s_{N N}}

= 27 GeV as a part of the STAR BES-II program, which is about a factor of 10 higher than BES-I 27 GeV data size. In this report, we present new measurements of charged particle production and the nuclear modification factor

R_{C P}

, from this new 27 GeV data set and compare them with the BES-I results. The new measurements extend the previous BES-I results to higher transverse momentum range, which allows better exploration of the jet quenching effects at low RHIC energies, and may help to understand the effects of the formation and properties of QGP at these energies. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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21 pages, 1673 KiB

Open AccessArticle

Simple Lévy α-Stable Model Analysis of Elastic pp and

p \bar{p}

Low-|t| Data from SPS to LHC Energies

by Tamás Csörgő, Sándor Hegyi and István Szanyi

Universe 2024, 10(3), 127; https://doi.org/10.3390/universe10030127 - 6 Mar 2024

Viewed by 1200

Abstract

A simple Lévy

α

-stable (SL) model is used to describe the data on elastic

p p

and

p \bar{p}

scattering at low-

| t |

from SPS energies up to LHC energies. The SL model is demonstrated to describe the data [...] Read more.

A simple Lévy

α

-stable (SL) model is used to describe the data on elastic

p p

and

p \bar{p}

scattering at low-

| t |

from SPS energies up to LHC energies. The SL model is demonstrated to describe the data with a strong non-exponential feature in a statistically acceptable manner. The energy dependence of the parameters of the model is determined and analyzed. The Lévy

α

parameter of the model has an energy-independent value of 1.959 ± 0.002 following from the strong non-exponential behavior of the data. We strengthen the conclusion that the discrepancy between TOTEM and ATLAS elastic

p p

differential cross section measurements arises only in the normalization and not in the shape of the distribution of the data as a function of t. We find that the slope parameter has different values for

p p

and

p \bar{p}

elastic scattering at LHC energies. This may be the effect of the odderon exchange or the jump in the energy dependence of the slope parameter in the energy interval 3 GeV

≲ \sqrt{s} ≲

4 GeV. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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9 pages, 2185 KiB

Open AccessCommunication

Heavy Flavor Physics at the sPHENIX Experiment

by Zhaozhong Shi

Universe 2024, 10(3), 126; https://doi.org/10.3390/universe10030126 - 6 Mar 2024

Cited by 1 | Viewed by 1397

Abstract

The sPHENIX experiment is a state-of-the-art jet and heavy flavor physics detector, which successfully recorded its first Au + Au collision data at 200 GeV at the Relativistic Heavy Ion Collider (RHIC). sPHENIX will provide heavy flavor physics measurements at RHIC, covering an [...] Read more.

The sPHENIX experiment is a state-of-the-art jet and heavy flavor physics detector, which successfully recorded its first Au + Au collision data at 200 GeV at the Relativistic Heavy Ion Collider (RHIC). sPHENIX will provide heavy flavor physics measurements at RHIC, covering an unexplored kinematic region and unprecedented precision, to probe the parton energy loss mechanism, parton transport coefficients in quark–gluon plasma, and the hadronization process under various medium conditions. At the center of sPHENIX, the monolithic active pixel sensor (MAPS)-based VerTeX detector (MVTX) is a high-precision silicon pixel detector. The MVTX provides excellent position resolution and the capability of operating in continuous streaming readout mode, allowing precise vertex determination and recording a large data sample, both of which are particularly crucial for heavy flavor physics measurements. In this work, we will show the general performance of heavy-flavor hadron reconstruction. In addition, we will discuss the commissioning experience with sPHENIX. Finally, we will provide the projection of b-hadron and jet observables and discuss the estimated constraints on theoretical models. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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9 pages, 1323 KiB

Open AccessArticle

First-Order Event Plane Correlated Directed and Triangular Flow from Fixed-Target Energies at RHIC-STAR

by Sharang Rav Sharma

Universe 2024, 10(3), 118; https://doi.org/10.3390/universe10030118 - 1 Mar 2024

Viewed by 1236

Abstract

We report the measurement of first-order event plane-correlated directed flow

(v_{1})

and triangular flow (

v_{3}

) for identified hadrons (

π^{\pm}

,

K^{\pm}

, and p), net particle (net-K, net-p), and light nuclei (d [...] Read more.

We report the measurement of first-order event plane-correlated directed flow

(v_{1})

and triangular flow (

v_{3}

) for identified hadrons (

π^{\pm}

,

K^{\pm}

, and p), net particle (net-K, net-p), and light nuclei (d and t) in Au + Au collisions at

\sqrt{s_{NN}}

= 3.2, 3.5, and 3.9 GeV in the fixed-target mode from the second phase of the beam energy scan (BES-II) program at RHIC-STAR. The

v_{1}

slopes at mid-rapidity for identified hadrons and net particles except

π^{+}

are found to be positive, implying the effect of dominant repulsive baryonic interactions. The slope of

v_{1}

for net-kaon undergoes a sign change from negative to positive at a lower collision energy compared to net-proton. An approximate atomic mass number scaling is observed in the measured

v_{1}

slopes of light nuclei at mid-rapidity, which favors the nucleon coalescence mechanism for the production of light nuclei. The

v_{3}

slope for all particles decreases in magnitude with increasing collision energy, suggesting a notable integrated impact of the mean-field, baryon stopping, and collision geometry at lower collision energies. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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5 pages, 225 KiB

Open AccessArticle

Understanding the Effect of Conserved Charges on the Coalescence Sum Rule of Directed Flow

by Kishora Nayak, Shu-Su Shi and Zi-Wei Lin

Universe 2024, 10(3), 112; https://doi.org/10.3390/universe10030112 - 1 Mar 2024

Viewed by 1241

Abstract

Recently, the rapidity-odd directed flow (

v_{1}

) of produced hadrons (

K^{-}

,

ϕ

,

\bar{p}

,

\bar{Λ}

,

{\bar{Ξ}}^{+}

,

Ω^{-}

, and

{\bar{Ω}}^{+}

) has been studied. Several combinations of these [...] Read more.

Recently, the rapidity-odd directed flow (

v_{1}

) of produced hadrons (

K^{-}

,

ϕ

,

\bar{p}

,

\bar{Λ}

,

{\bar{Ξ}}^{+}

,

Ω^{-}

, and

{\bar{Ω}}^{+}

) has been studied. Several combinations of these produced hadrons, with very small mass differences but differences in the net electric charge (

Δ q

) and net strangeness (

Δ S

) on the two sides, have been considered. A difference in

v_{1}

between the two sides of these combinations (

Δ v_{1}

) has been proposed as a consequence of the electromagnetic field produced in relativistic heavy-ion collisions, especially if

Δ v_{1}

increases with

Δ q

. Our study is performed to understand the effect of the coalescence sum rule (CSR) on

Δ v_{1}

. We point out that the CSR leads to

Δ v_{1} = c_{q} Δ q + c_{S} Δ S

, where the coefficients

c_{q}

and

c_{S}

reflect the

Δ v_{1}

of produced quarks. Equivalently, one can write

Δ v_{1} = c_{q} Δ q + c_{B} Δ B

, involving the difference in the net baryon number

Δ B

, where the CSR gives

c_{B} = - 3 c_{S}

. We then propose two methods to extract the coefficients for the

Δ q

and

Δ S

dependences of

Δ v_{1}

. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

12 pages, 733 KiB

Open AccessArticle

Two-Pomeron Interaction

by Luis Cancino Arancibia and Carlos Contreras

Universe 2024, 10(3), 103; https://doi.org/10.3390/universe10030103 - 20 Feb 2024

Viewed by 1309

Abstract

We study the interaction of two discrete pomeron fields while considering mass mixing and the general structure of the interaction potential for pomerons within the framework for a functional renormalization group analysis of Reggeon field theory. We find fixed points from the zeros [...] Read more.

We study the interaction of two discrete pomeron fields while considering mass mixing and the general structure of the interaction potential for pomerons within the framework for a functional renormalization group analysis of Reggeon field theory. We find fixed points from the zeros of the beta function establishing the existence of three groups of solutions: the first corresponds to two uncoupled pomerons, the second is a solution known as a “pomeron–odderon” interaction, and the final is a real general solution with an interaction potential. We also study its universal properties around this fixed point. This analysis allows for a discussion for the first time on the mixing of two pomerons through renormalization flow paths from the ultraviolet to the non-perturbative infrared regions. Finally, we comment on its role in high-energy scattering. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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9 pages, 384 KiB

Open AccessCommunication

Pion Interferometry with Lévy-Stable Sources in

\sqrt{s_{N N}}

= 200 GeV Au + Au Collisions at STAR

by Dániel Kincses

Universe 2024, 10(3), 102; https://doi.org/10.3390/universe10030102 - 20 Feb 2024

Cited by 6 | Viewed by 1540

Abstract

Measurements of femtoscopic correlations in high-energy heavy-ion collisions are used to unravel the space–time structure of the particle-emitting source (the quark–gluon plasma). Recent results indicate that the pion pair source exhibits a power law behavior and can be described well by a Lévy [...] Read more.

Measurements of femtoscopic correlations in high-energy heavy-ion collisions are used to unravel the space–time structure of the particle-emitting source (the quark–gluon plasma). Recent results indicate that the pion pair source exhibits a power law behavior and can be described well by a Lévy distribution. In this study, Lévy fits were applied to the measured one-dimensional two-pion correlation functions in Au + Au collisions at

\sqrt{s_{N N}}

= 200 GeV. The three extracted source parameters are the Lévy scale parameter, R, which relates to the size of the source; the correlation strength parameter,

λ

; and the Lévy exponent,

α

, which characterizes the power law tail of the source. In this paper, we report the current status of the analysis of the extracted Lévy source parameters and present their dependence on average transverse mass,

m_{T}

, and on centrality. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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12 pages, 337 KiB

Open AccessArticle

Proposal for an Electromagnetic Mass Formula for the X17 Particle

by Sándor Varró

Universe 2024, 10(2), 86; https://doi.org/10.3390/universe10020086 - 12 Feb 2024

Viewed by 1448

Abstract

Recent observations of anomalous angular correlations of electron–positron pairs in several nuclear reactions have indicated the existence of a hypothetical neutral boson of rest mass ~17 MeV/c², called the X17 particle. Similarly, one has interpreted an independent set of experiments [...] Read more.

Recent observations of anomalous angular correlations of electron–positron pairs in several nuclear reactions have indicated the existence of a hypothetical neutral boson of rest mass ~17 MeV/c², called the X17 particle. Similarly, one has interpreted an independent set of experiments on photon pair spectra around the invariant mass ~38 MeV/c², by assuming the existence of the so-called E38 particle. In the present paper, we derive analytical mass formulas for the X17 particle and the E38 particle, on the basis of quantum electrodynamics. We shall use the exact solutions of the Dirac equation of the joint system of a charged particle and plane waves of the quantized electromagnetic radiation. When these solutions are applied to a proton, they lead to dressed radiation quanta with a rest mass of 17.0087 MeV/c², which may be identified with the X17 vector bosons. A similar consideration, applied to the udd quarks of the neutron, yields dressed quanta, whose mass equals 37.9938 MeV/c², corresponding to the E38 particle. These formulas, besides the Sommerfeld fine structure constant and the masses of the nucleons, do not contain any adjustable parameters. The present analysis also delivers the value 0.846299 fm for the proton radius. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

9 pages, 423 KiB

Open AccessCommunication

Coulomb-Nuclear Interference in Polarized pA Scattering

by Boris Kopeliovich, Michal Krelina and Irina Potashnikova

Universe 2024, 10(2), 63; https://doi.org/10.3390/universe10020063 - 31 Jan 2024

Cited by 2 | Viewed by 1009

Abstract

We made the first attempt to understand the observed unusual t dependence of single-spin asymmetry observed in the HJET experiment at RHIC. Usually, the interaction of hadrons is presented as a long-range Coulomb interaction and a short-range strong interaction with Coulomb corrections. Such [...] Read more.

We made the first attempt to understand the observed unusual t dependence of single-spin asymmetry observed in the HJET experiment at RHIC. Usually, the interaction of hadrons is presented as a long-range Coulomb interaction and a short-range strong interaction with Coulomb corrections. Such a division gives rise to a Coulomb phase of the hadronic term. Conversely, here we consider short-range hadronic interaction as a correction to the long-range electromagnetic term, i.e., we treat it as an absorptive correction. This significantly affects the Coulomb-nuclear interference, which is a source of single-spin azimuthal asymmetry at small angles. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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12 pages, 441 KiB

Open AccessArticle

Femtoscopy with Lévy Sources from SPS through RHIC to LHC

by Máté Csanád and Dániel Kincses

Universe 2024, 10(2), 54; https://doi.org/10.3390/universe10020054 - 23 Jan 2024

Cited by 9 | Viewed by 1371

Abstract

Femtoscopy is a unique tool to investigate the space-time geometry of the matter created in ultra-relativistic collisions. If the probability density distribution of hadron emission is parametrized, then the dependence of its parameters on particle momentum, collision energy, and collision geometry can be [...] Read more.

Femtoscopy is a unique tool to investigate the space-time geometry of the matter created in ultra-relativistic collisions. If the probability density distribution of hadron emission is parametrized, then the dependence of its parameters on particle momentum, collision energy, and collision geometry can be given. In recent years, several measurements came to light that indicated the adequacy of assuming a Lévy-stable shape for the mentioned distribution. In parallel, several new phenomenological developments appeared, aiding the interpretation of the experimental results or providing tools for the measurements. In this paper, we discuss important aspects of femtoscopy with Lévy sources in light of some of these advances, including phenomenological and experimental ones. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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8 pages, 7536 KiB

Open AccessCommunication

Pacific Ocean Neutrino Experiment

by Paweł Malecki

Universe 2024, 10(2), 53; https://doi.org/10.3390/universe10020053 - 23 Jan 2024

Cited by 1 | Viewed by 1817

Abstract

Following the breakthrough discoveries of very-high-energy neutrinos of astrophysical origin by IceCube, a new field of research, neutrino astronomy, was established in the previous decade. Even though two extragalactic point sources of such neutrinos have been identified by now, TXS 0506+056 and NGC [...] Read more.

Following the breakthrough discoveries of very-high-energy neutrinos of astrophysical origin by IceCube, a new field of research, neutrino astronomy, was established in the previous decade. Even though two extragalactic point sources of such neutrinos have been identified by now, TXS 0506+056 and NGC 1068, the origin and processes of the creation of astrophysical neutrinos are still mostly unexplored. To advance quickly in this new field, more neutrino telescopes are needed. This article describes the current status and plans for the development of the Pacific Ocean Neutrino Experiment (P-ONE), which is under construction in the Pacific Ocean near Vancouver Island. The deployment of P-ONE is expected to start in 2025, exploiting the already available deep-sea infrastructure provided by Ocean Networks Canada. P-ONE will complement the existing IceCube, Baikal-GVD, and KM3NeT neutrino telescopes not only with its large detection volume, but also by providing insight into the southern celestial hemisphere, where the central region of the Galactic Plane is located. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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37 pages, 436 KiB

Open AccessArticle

On the Implications of |U_μi| = |U_τi| in the Canonical Seesaw Mechanism

by Jianlong Lu, Aik Hui Chan and Choo Hiap Oh

Universe 2024, 10(1), 50; https://doi.org/10.3390/universe10010050 - 21 Jan 2024

Cited by 1 | Viewed by 1426

Abstract

In the PMNS matrix, the relation

| U_{μ i} | = | U_{τ i} |

(with

i = 1, 2, 3

) is experimentally favored at the present stage. The possible implications of this relation on some [...] Read more.

In the PMNS matrix, the relation

| U_{μ i} | = | U_{τ i} |

(with

i = 1, 2, 3

) is experimentally favored at the present stage. The possible implications of this relation on some hidden flavor symmetry has attracted a lot of interest in the neutrino community. In this paper, we analyze the implications of

| U_{μ i} | = | U_{τ i} |

(with

i = 1, 2, 3

) in the context of the canonical seesaw mechanism. We also show that the minimal

μ - τ

symmetry proposed in JHEP 06 (2022) 034 is a possible but not necessary reason for the above-mentioned relation. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

12 pages, 2703 KiB

Open AccessCommunication

Conserved Charge Fluctuations from RHIC BES and FXT

by Toshihiro Nonaka

Universe 2024, 10(1), 49; https://doi.org/10.3390/universe10010049 - 19 Jan 2024

Viewed by 1318

Abstract

Cumulants up to the sixth-order of the net-particle multiplicity distributions were measured at RHIC for the Beam Energy Scan and fixed-target program, from which we obtained some interesting hints on the phase structure of the QCD matter. In this article, we present recent [...] Read more.

Cumulants up to the sixth-order of the net-particle multiplicity distributions were measured at RHIC for the Beam Energy Scan and fixed-target program, from which we obtained some interesting hints on the phase structure of the QCD matter. In this article, we present recent experimental results on (net-)proton cumulants and discuss current interpretations on the QCD critical point and the nature of the phase transition. We will also report recent results for measurements of the bayron-strangeness correlations, which were measured with the newly developed analysis technique to remove the effect from the combinatorial backgrounds for hyperon reconstruction. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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10 pages, 586 KiB

Open AccessArticle

Scaling Behaviour of dN/dy in High-Energy Collisions

by Gábor Kasza and Tamás Csörgő

Universe 2024, 10(1), 45; https://doi.org/10.3390/universe10010045 - 17 Jan 2024

Cited by 1 | Viewed by 1330

Abstract

From a recently found family of analytic, finite and accelerating 1+1-dimensional solutions to perfect fluid relativistic hydrodynamics, we derive simple and powerful formulae to describe the rapidity and pseudorapidity density distributions. By introducing a new scaling function, we notice that the rapidity distribution [...] Read more.

From a recently found family of analytic, finite and accelerating 1+1-dimensional solutions to perfect fluid relativistic hydrodynamics, we derive simple and powerful formulae to describe the rapidity and pseudorapidity density distributions. By introducing a new scaling function, we notice that the rapidity distribution data of the different experiments all collapse into a single curve. This data-collapsing (or -scaling) behaviour in the rapidity distributions suggests that high-energy

p + p

collisions may be described as collective systems. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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16 pages, 846 KiB

Open AccessArticle

Polarization Measurements of p^↑ and ³He^↑ Beams at RHIC and Future EIC Using the Polarized Atomic Hydrogen Gas Jet Target

by A. A. Poblaguev

Universe 2024, 10(1), 32; https://doi.org/10.3390/universe10010032 - 11 Jan 2024

Cited by 2 | Viewed by 1182

Abstract

At the Relativistic Heavy Ion Collider (RHIC), the Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is employed for the precise measurement of the absolute transverse (vertical) polarization of proton beams, achieving low systematic uncertainties of approximately [...] Read more.

At the Relativistic Heavy Ion Collider (RHIC), the Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is employed for the precise measurement of the absolute transverse (vertical) polarization of proton beams, achieving low systematic uncertainties of approximately

σ_{P}^{syst} / P \leq 0.5 %

. The acquired experimental data not only facilitated the determination of single

A_{N} (t)

and double

A_{NN} (t)

spin analyzing powers for 100 and 255 GeV proton beams, but also revealed a non-zero Pomeron spin-flip contribution through a Regge fit. Preliminary results obtained for forward inelastic

p^{↑} p

and elastic

p^{↑} A

analyzing powers will be discussed. The success of the HJET at RHIC suggests its potential application for proton beam polarimetry at the upcoming Electron–Ion Collider (EIC), aiming for an accuracy of 1%. Moreover, the provided analysis indicates that the RHIC HJET target can serve as a tool for the precision calibration, with the required accuracy, of the

^{3}

He beam polarization at the EIC. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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13 pages, 625 KiB

Open AccessArticle

Exploring Global Polarization Splitting in Au+Au Collisions at

\sqrt{s_{NN}} = 19.6

GeV Using Viscous Hydrodynamic Model CLVisc

by Shasha Ye, Xuefei Yuan and Zefang Jiang

Universe 2024, 10(1), 8; https://doi.org/10.3390/universe10010008 - 25 Dec 2023

Viewed by 1519

Abstract

We present a systematic study of the global polarization of

Λ

and

\bar{Λ}

hyperons in Au+Au collisions at

\sqrt{s_{NN}} = 19.6

GeV using the viscous hydrodynamic model CCNU-LBNL-Viscous hydrodynamic model (CLVisc) with a modified 3D optical Glauber model initial condition. The [...] Read more.

We present a systematic study of the global polarization of

Λ

and

\bar{Λ}

hyperons in Au+Au collisions at

\sqrt{s_{NN}} = 19.6

GeV using the viscous hydrodynamic model CCNU-LBNL-Viscous hydrodynamic model (CLVisc) with a modified 3D optical Glauber model initial condition. The global polarization splitting as a function of transverse momentum and rapidity is investigated. It is shown that the magnitude of the net baryon density and its longitudinal titled geometry at the initial stage both have significant effects on the global polarization splitting of

Λ

and

\bar{Λ}

hyperons. Specifically, an increase in the magnitude of the net baryon density leads to a corresponding minor increase in the global polarization splitting. Similarly, alterations in the tilted geometry of net baryon density results in significant changes in the splitting of the global polarization. Full article

(This article belongs to the Special Issue Multiparticle Dynamics)

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