Inelastic Proton Research Articles

Measurements of higher-order cumulants of multiplicity and net-electric charge distributions in inelastic proton–proton interactions by NA61/SHINE

This paper presents the energy dependence of multiplicity and net-electric charge fluctuations in p+p interactions at beam momenta 20, 31, 40, 80, and 158 GeV/c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{ Ge }\\hspace{-1.00006pt}\ ext{ V }\\!/\\!c$$\\end{document}. Results are corrected for the experimental biases and quantified with the use of cumulants and factorial cumulants. Cumulant ratios are an essential tool in the search for the critical point of strongly interacting matter in heavy ion collisions. Measurements performed in p+p interactions provide a vital baseline estimation in these studies. The measured signals are compared with the string hadronic models Epos1.99 and FTFP-BERT.

Ab initio leading order effective potential for elastic proton scattering based on the symmetry-adapted no-core shell model

<i>Ab initio</i> leading order effective potential for elastic proton scattering based on the symmetry-adapted no-core shell model

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

Evaluating the H(x,s|pp) scaling function of elastic proton–proton (pp) collisions from recent TOTEM data at s=8 TeV and comparing it with the same function of elastic proton–antiproton (pp¯) data of the D0 collaboration at 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 pp scattering data at 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.

Coulomb-nuclear interference in elastic proton scattering in the eikonal approach

We find exact solution in the Cahn eikonal model, which describes Coulomb-nuclear interference in elastic scattering of charged hadrons. The cases of both point-like and extended particles equipped with electromagnetic form factors are considered. According to the solution obtained the Coulomb-nuclear contributions are not exponentiated and cannot be added to the Coulomb phase. At the same time, the O(α)-approximation of the amplitude is ambiguous, which makes it unsuitable for data processing.

Dark photon production via elastic proton bremsstrahlung with non-zero momentum transfer

We explore hypothetical vector particles, dark photons γ′, which mix with the Standard Model photons and thus mediate interactions with charged particles into the hidden sector. We study the elastic proton bremsstrahlung of dark photons with masses 0.4–1.8 GeV, relevant for direct searches with proton accelerators. A key feature of our calculation is that it explicitly considers the non-zero momentum transfer between protons in the process pp → ppγ′. We compare the obtained differential and full bremsstrahlung cross sections with the results of other authors. Our calculation agrees well (up to 3–9% corrections) with the Weizsacker-Williams approximation that confirms its applicability for proton beams. Then we refine predictions for the dark photon production with proton beams of energy 30 GeV, 70 GeV, 120 GeV and 400 GeV relevant for past, present and future experiments considered in literature.

γ-ray spectroscopic study of self-conjugate 10B nucleus with inelastic proton scattering

A γ-ray spectroscopic study of 10B is reported. Excited states in 10B were populated in inelastic proton scattering and their γ-decays were measured with the ELIFANT array, a state-of-the-art spectrometer with large volume LaBr3:Ce and CeBr3 detectors placed in anti-Compton shields and having unprecedented efficiency for high-energy γ rays. A few weak transitions were observed in the experiment, namely M3 transition between Jπ, T = 0+1, 1 isobaric analog state to the Jπ, T = 3+1,0 ground state and E2 transition between the Jπ, T = 2+1,0 state and the isobaric analog state. The results are compared to a new set of ab initio no-core shell model calculation using the newest version of the local position-space chiral N3LO nucleon-nucleon interaction, which correctly reproduces the spectrum of the excited states in 10B, a problem of the theory in previous years.

Elastic proton–neutron and antiproton–neutron scattering in holographic QCD

The total and differential cross sections of the elastic proton–neutron and antiproton–neutron scattering are studied in a holographic QCD model, focusing on the Regge regime. Taking into account the Pomeron and Reggeon exchange, which are described by the Reggeized spin-2 glueball and vector meson propagator respectively, those cross sections are obtained. It is presented that the currently available experimental data of the total cross sections can be well described within the model. Once a single adjustable parameter is determined with the total cross section data, the differential cross sections can be calculated without any additional parameters. Although the available differential cross section data are limited, it is found that our predictions are consistent with those.

Studying differential cross section for elastic proton scattering by a tensor model

Previous studies have shown the reliability of the Bayesian Gaussian CANDECOMP/PARAFAC tensor decomposition (BGCP) algorithm in predicting the independent fission yields and evaluating global uncertainty of the data. This work proposes to apply the BGCP algorithm for the purpose of predicting and evaluating the differential cross section for elastic proton scattering. The tensor model is developed by training with the experimental data of elastic proton scattering from the EXFOR database. The Root Mean Square Error is used to evaluate the experimental data and search for potential errors and omissions in EXFOR, in order to identify outlying data of 98Mo, 100Mo, 144Sm and 209Bi. After the revision for the outlying data in EXFOR, the reproduced values for 144Sm are compared with the remaining controversial entries. Besides, the predicted data for 9C are compared with the published data not available in EXFOR. The results demonstrate that the tensor model can make reasonable predictions and has a role to play in evaluating the quality of elastic proton scattering data. The tensor model may become a powerful tool for nuclear data evaluation in EXFOR.

Shape analysis of the 4.44 MeV γ-ray line complex produced in inelastic proton scattering off 12C over the indent energy range of Ep = 30−200 MeV

We report γ-ray spectra for the line observed at Eγ = 4.44 MeV in our previous experiments at iThemba LABS’ SSC facility using 30 - 200 MeV proton beams to irradiate a natC target. It is actually a complex composed of several lines of interest broadened by Doppler effect. In addition to the dominant 4.439 MeV line of 12C, two other lines at Eγ = 4.319 and 4.445 MeV assigned to 11C and 11B, respectively, are significant components of this complex. The analysis of its line shapes based on nuclear reaction models is the main topic of this contribution.

Extraction of neutron density distributions from high-statistics coherent elastic neutrino-nucleus scattering data

Forthcoming fixed-target coherent elastic neutrino-nucleus scattering experiments aim at measurements with O(tonne)-scale detectors and substantially reduced systematic and statistical uncertainties. With such high quality data, the extraction of point-neutron distributions mean-square radii requires a better understanding of possible theoretical uncertainties. We quantify the impact of single-nucleon electromagnetic mean-square radii on the weak-charge form factor and compare results from weak-charge form factor parametrizations and weak-charge form factor decompositions in terms of elastic vector proton and neutron form factors, including nucleon form factors Q-dependent terms up to order Q2. We assess as well the differences arising from results derived using weak-charge form factor decompositions in terms of elastic vector proton and neutron form factors and a model-independent approach based solely on the assumption of spherically symmetric nuclear ground state. We demonstrate the impact of the main effects by assuming pseudo-data from a one-tonne LAr detector and find that, among the effects and under the assumptions considered in this paper, weak-charge form factor parametrizations and weak-charge form factor decompositions in terms of elastic vector proton and neutron form factors enable the extraction of the Ar40 point-neutron distribution mean-square radius with a ∼15% accuracy. With a substantial reduction of the beam-related neutron and steady-state backgrounds a ∼1% precision extraction seems feasible, using either of the two approaches.

Lévy α-Stable Model for the Non-Exponential Low-|t| Proton–Proton Differential Cross-Section

It is known that the Real Extended Bialas–Bzdak (ReBB) model describes the proton–proton (pp) and proton–antiproton (pp¯) differential cross-section data in a statistically non-excludible way, i.e., with a confidence level greater than or equal to 0.1% in the center of mass energy range 546 GeV ≤s≤8 TeV and in the squared four-momentum transfer range 0.37 GeV2 ≤ −t ≤ 1.2 GeV2. Considering, instead of Gaussian, a more general Lévy α-stable shape for the parton distributions of the constituent quark and diquark inside the proton and for the relative separation between them, a generalized description of data is obtained, where the ReBB model corresponds to the α=2 special case. Extending the model to α&lt;2, we conjecture that the validity of the model can be extended to a wider kinematic range, in particular, to lower values of the four-momentum transfer −t. We present the formal Lévy α-stable generalization of the Bialas–Bzdak model and show that a simplified version of this model can be successfully fitted, with α&lt;2, to the non-exponential, low −t differential cross-section data of elastic proton–proton scattering at s=8 TeV.

Interacting Colour Strings Approach in Modelling of Rapidity Correlations

In this paper, using the concept of multi-pomeron exchange, we develope a Monte Carlo model of interacting quark–gluon strings acting as particle-emitting sources aimed at describing inelastic proton–proton interactions at high energies. The implemented 3D (three-dimensional) dynamics of colour string formation resulted in their finite length in the rapidity space and in the fluctuating event-by-event spatial density. Thus, this results in string cluster formation because of the fusion mechanism and the appearance of long-range multiplicity and mean transverse momentum (mean-pT) correlations in rapidity. We study, via the pseudorapidity dependence, the sensitivity to the details of the 3D dynamical formation of strings for several observables such as the forward–backward correlation coefficient value, strongly intensive quantity, Σ, and the “almost” strongly intensive observable, the variance, σC2, of the distribution of the asymmetry coefficient, C. The strongly intensive quantity Σ is used in this study to suppress trivial statistical fluctuations in the number of particles emitting similar types of sources and to reveal the intrinsic fluctuations of a single source. We demonstrate the connection between Σ and such often used observables as cumulants, factorial cumulants, and σC2. We stress the importance of the contribution of “short” strings and the event asymmetry of the initial conditions on the long-range correlation measures. We argue that string cluster formation because of the fusion mechanism explains the collective effects seen in multiplicity and transverse momentum–multiplicity, ⟨pT⟩–N, long-range correlation functions.

Hexadecapole strength in the rare isotopes 74,76Kr

In the Ge-Sr mass region, isotopes with neutron number N≤40 are known to feature rapid shape changes with both nucleon number and angular momentum. To gain new insights into their structure, inelastic proton scattering experiments in inverse kinematics were performed on the rare isotopes 74,76Kr. This work focuses on observables related to the Jπ=41+ states of the Kr isotopes and, in particular, on the hexadecapole degree of freedom. By performing coupled-channels calculations, hexadecapole deformation parameters β4 were determined for the Jπ=41+ states of 74,76Kr from inelastic proton scattering cross sections. Two possible coupled-channels solutions were found. A comparison to predictions from nuclear energy density functional theory, employing both non-relativistic and relativistic functionals, clearly favors the large, positive β4 solutions. These β4 values are unambiguously linked to the well deformed prolate configuration. Given the β2−β4 trend, established in this work, it appears that β4 values could provide a sensitive measure of the nuclear shell structure.

Matter radius of the doubly-magic ^{56}Ni measured in a storage ring

The matter radius of the doubly magic ^{56}Ni was extracted from a measurement of the differential cross section by employing, for the first time, elastic proton scattering in inverse kinematics with a radioactive beam at E_{kin}=390.2 MeV/nucleon circulating in a storage ring and passing an internal hydrogen gas-jet target with a revolution frequency of around 2 MHz. The novel experimental scheme is based on UHV-compatible Si detectors operated as active vacuum windows, which were implemented in the ESR storage ring at GSI. A matter radius <r_{m}^{2}>^{1/2}=3.74^{+0.03}_{-0.06} fm was extracted for the doubly-magic self-conjugate nucleus ^{56}Ni.

Planck formula for the gluon parton distribution in the proton

In this paper, we describe the gluon parton distribution function (PDF) in the proton, deduced by data from the ATLAS and HERA experiments, in the framework of the parton statistical model. The best fit parameters involved in the Planck formula that describes the gluon distribution are consistent with the results obtained from analysis of LHC deep inelastic proton–proton scattering processes. Remarkably, the agreement between the statistical model and the experimental gluon distributions is obtained with the same value of the “temperature” parameter [Formula: see text] found by fitting the valence parton distributions from deep inelastic scattering. This result corroborates the validity of the statistical approach in the gluon sector.

Test of the TMD gluon density in a proton with the longitudinal structure function FL(x,Q2)

We investigate the dependence of the deep inelastic proton structure function FL(x,Q2) on different forms of the transverse momentum dependent (TMD, or unintegrated) gluon distribution. We present a comparison of theoretical results with the latest experimental data taken by the H1 and ZEUS Collaborations at HERA. We demonstrate that these data, despite of having quite large uncertainties, can test different kinds of the gluon TMD in a proton. Moreover, different phenomenological models at low x could be tested by future experiments on deep inelastic scattering.

Supernova connection of unidentified ultra-high-energy gamma-ray source LHAASO J2108+5157

ABSTRACT We present a simple phenomenological model of hadronic interaction between protons accelerated in an old supernova remnant (SNR) and cold protons situated within the associated molecular clouds (MCs). The accelerated protons from the old SNR escaped the SNR shock front, and got injected into the MCs at an earlier time, producing ultra-high-energy gamma-rays and neutrinos through inelastic proton–proton interaction. We also take into account the acceleration and subsequent escape of electrons from the SNR shock front. The escaped electrons produce gamma-rays through various radiative cooling mechanisms, after getting injected into the MCs. We use the model discussed in this letter to explain the multiwavelength spectral energy distribution of unidentified Galactic ultra-high-energy gamma-ray source LHAASO J2108+5157. We also discuss the feasibility of applying this model in other cases as well. Future observations can test the viability of the model discussed in this letter, which will in turn confirm that the SNRs can, in fact, accelerate particles up to PeV energies.

Dependence of Freeze-Out Parameters on Collision Energies and Cross-Sections

We analyzed the transverse momentum spectra (pT) reported by the NA61/SHINE and NA49 experiments in inelastic proton–proton (pp) and central Lead–Lead (Pb−Pb), Argon–Scandium (Ar−Sc), and Beryllium–Beryllium (Be−Be) collisions with the Blast-wave model with Boltzmann–Gibbs (BWBG) statistics. The BGBW model was in good agreement with the experimental data. We were able to extract the transverse flow velocity (βT), the kinetic freeze-out temperature (T0), and the kinetic freeze-out volume (V) from the pT spectra using the BGBW model. Furthermore, we also obtained the initial temperature (Ti) and the mean transverse momentum (&lt;pT&gt;) by the alternative method. We observed that T0 increases with increasing collision energy and collision cross-section, representing the colliding system’s size. The transverse flow velocity was observed to remain invariant with increasing collision energy, while it showed a random change with different collision cross-sections. In the same way, the kinetic freeze-out volume and mean transverse momentum increased with an increase in collision energy or collision cross-section. The same behavior was also seen in the freeze-out temperature, which increased with increasing collision cross-sections. At chemical freeze-out, we also determined both the chemical potential and temperature and compared these with the hadron resonance gas model (HRG) and different experimental data. We report that there is an excellent agreement with the HRG model and various experiments, which reveals the ability of the fit function to manifest features of the chemical freeze-out.

Nuclear level densities and γ-ray strength functions of 120,124Sn and their application in astrophysics

Nuclear level densities (NLDs) and γ-ray strength functions (GSFs)of 120;124Sn have been extracted with the Oslo method and additionally constrained with the novel Shape method. The GSFs were found to be in excellent agreement with the strengths from the inelastic relativistic proton scattering experiment. This comparison suggests the validity of the Brink-Axel hypothesisused as one of the key assumptions in astrophysical calculations. The extracted NLDs and GSFs were further used as experimental inputs to constrain the Maxwellian-averaged cross sections (MACS) for the radiative neutron capture process 119;123Sn (n, γ)120;124Sn using the the nuclear reaction code TALYS.

Model-independent Odderon Results Based on TOTEM data on Elastic Proton–Proton Scattering at 8 TeV

Model-independent Odderon Results Based on TOTEM data on Elastic Proton–Proton Scattering at 8 TeV