Baryon Production Research Articles

Universal energy dependence of measured temperatures for baryons produced in heavy-ion collisions

From the data on baryon production in heavy-ion collisions it is shown that a set of measurable functions exist, one for each baryon type, that depend exponentially on transverse momenta up to the maximum values detected for all collision energies ranging from the low end of RHIC BES to the high end of CERN LHC. The implied temperatures satisfy a scaling law in collision energy with a universal exponent for all baryon types which is the novel discovery. A self-similar thermal source is implied. Furthermore, it is shown how the scaling behavior depends on centralities. Those features in the data are related to simple properties of light and strange quarks by use of the recombination model. Prediction of $\phi$ meson production is made and then verified by existing data.

First Measurement of Quasielastic Λ Baryon Production in Muon Antineutrino Interactions in the MicroBooNE Detector.

We present the first measurement of the cross section of Cabibbo-suppressed Λ baryon production, using data collected with the MicroBooNE detector when exposed to the neutrinos from the main injector beam at the Fermi National Accelerator Laboratory. The data analyzed correspond to 2.2×10^{20} protons on target running in neutrino mode, and 4.9×10^{20} protons on target running in anti-neutrino mode. An automated selection is combined with hand scanning, with the former identifying five candidate Λ production events when the signal was unblinded, consistent with the GENIE prediction of 5.3±1.1 events. Several scanners were employed, selecting between three and five events, compared with a prediction from a blinded MonteCarlo simulation study of 3.7±1.0 events. Restricting the phase space to only include Λ baryons that decay above MicroBooNE's detection thresholds, we obtain a flux averaged cross section of 2.0_{-1.7}^{+2.2}×10^{-40} cm^{2}/Ar, where statistical and systematic uncertainties are combined.

STUDYING THE RESONANCE PRODUCTION CROSS-SECTION OF THE HEAVY VECTORS WITHIN HEAVY VECTOR TRIPLET MODEL

In the context of TeV-scale extensions of the Standard Model both the experimental data and the construction of phenomenological models for the new heavy bosons searches are used by us. Heavy particles are predicted by the Simplified Model to describe only the on-shell resonance, have to be compared with LHC data. Bosons V’ created and decay according to the process pp->V’->Vh (V=W, Z) have certain properties that can be modeled within the Heavy Vector Triplet model using the Madgraph computer program. We have calculated the production cross sections of heavy particles using the experimental constraints in the parameter space (cH, cF) imposed on the benchmark scenario. The nature of the functional dependence of the cross section on the mass of the new boson, as well as the mechanism for the heavy particle production is studied with variation of the model parameters.

Decay law of magnetic turbulence with helicity balanced by chiral fermions

In plasmas composed of massless electrically charged fermions, chirality can be interchanged with magnetic helicity while preserving the total chirality through the quantum chiral anomaly. The decay of turbulent energy in plasmas such as those in the early Universe and compact stars is usually controlled by certain conservation laws. In the case of zero total chirality, when the magnetic helicity density balances with the appropriately scaled chiral chemical potential to zero, the total chirality no longer determines the decay. We propose that in such a case, an adaptation to the Hosking integral, which is conserved in nonhelical magnetically dominated turbulence, controls the decay in turbulence with helicity balanced by chiral fermions. We show, using a high resolution numerical simulation, that this is indeed the case. The magnetic energy density decays and the correlation length increases with time just like in nonhelical turbulence with vanishing chiral chemical potential. But here, the magnetic helicity density is nearly maximum and shows a scaling with time t proportional to t−2/3. This is unrelated to the t−2/3 decay of magnetic energy in fully helical magnetic turbulence. The modulus of the chiral chemical potential decays in the same fashion. This is much slower than the exponential decay previously expected in theories of asymmetric baryon production from the hypermagnetic helicity decay after axion inflation.Received 1 February 2023Accepted 4 April 2023DOI:https://doi.org/10.1103/PhysRevResearch.5.L022028Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAstrophysical fluid dynamicsCosmologyMagnetohydrodynamic turbulenceGravitation, Cosmology & AstrophysicsPlasma PhysicsFluid Dynamics

The Catalytic Role of Electrons and Positrons in the Synthesis of Chemicals and of Hadrons

We discuss the similarities and differences between catalysis/electrocatalysis of chemical processes, such as ammonia synthesis or H2O electrolysis on one hand, and of nuclear catalytic processes, commonly called baryosynthesis, such as the synthesis of neutrons and protons from quarks, on the other. In chemical synthesis the underlying forces are well known to be electrostatic in nature while in the synthesis of hadrons or nuclei from quarks (known as hadronization or nucleosynthesis) the underlying forces are known as the Strong nuclear forces, whereas if electrons are also involved, as Weak nuclear forces. Here we discuss for the first time from a catalytic viewpoint the importance of some recent developments in our understanding of the structure and synthesis of hadrons via a model entitled Rotating Lepton Model (RLM), which is quite similar to the Bohr model of the H atom used in Chemistry but which has shown that the Strong Force is a gravitational force between three very fast (relativistic) neutrinos, rotating symmetrically on a circular orbit, whose gravitational masses and gravitational attraction increases dramatically with increasing rotational speed, according to the theory of Special Relativity (SR), thus reaching the masses of quarks and the value of the Strong Force respectively. We show that, interestingly, positrons and electrons, which quite often play a very important and well established catalytic role in chemical synthesis due to their electrical charge, also play an equally important and central catalytic role in nuclear synthesis due to their enormous mass, relative to the mass of the neutrinos, and the concomitant dramatic acceleration of neutrinos to ultrarelativistic speeds and huge mass increase, resulting to enhanced very strong gravitational binding between them which reaches the value of the Strong Force. Consequently, electrons and positrons are the dual, electrostatic and gravitational, catalysts of our Universe for the production of chemicals and baryons.

Impact of QCD uncertainties on antiproton spectra from dark-matter annihilation

Dark-matter particles that annihilate or decay can undergo complex sequences of processes, including strong and electromagnetic radiation, hadronisation, and hadron decays, before particles that are stable on astrophysical time scales are produced. Antiprotons produced in this way may leave footprints in experiments such as AMS–02. Several groups have reported an excess of events in the antiproton flux in the rigidity range of 10–20 GV. However, the theoretical modeling of baryon production is not straightforward and relies in part on phenomenological models in Monte Carlo event generators. In this work, we assess the impact of QCD uncertainties on the spectra of antiprotons from dark-matter annihilation. As a proof-of-principle, we show that for a two-parameter model that depends only on the thermally-averaged annihilation cross section (〈σv〉) and the dark-matter mass (Mχ ), QCD uncertainties can affect the best-fit mass by up to ∼ 14% (with large uncertainties for large DM masses), depending on the choice of Mχ and the annihilation channel (bb̅ or W + W -), and 〈σv〉 by up to ∼ 10%. For comparison, changes to the underlying diffusion parameters are found to be within 1%–5%, and the results are also quite resilient to the choice of cosmic-ray propagation model. These findings indicate that QCD uncertainties need to be included in future DM analyses. To facilitate full-fledged analyses, we provide the spectra in tabulated form including QCD uncertainties and code snippets to perform mass interpolations and quick DM fits. The code can be found in this GitHub [1] repository.

Tcs and Tcs¯ Family Production in Multi-Production Processes

The production mechanism of multiquark exotic hadrons in high energy multiproduction processes lies in the structure of the relevant exotic hadrons as well as in some important aspects of high energy scattering, such as multi-parton interactions, underlying events, etc. At mass pole around 2900 MeV, a family of open charm tetraquarks, Tcss and Tcs¯s, are observed in B decay. They are also suitable for study in multiproduction processes to obtain more information on their structure. If these resonances are produced as compact four-quark states, one can predict the production properties based on the similarities in their production mechanism to those of Ξc, Σc, and Λc. Physics implies that the colour and baryon number fluctuations of the preconfinement system in high energy scattering can enhance both the baryon and four-quark state production rates via ‘diquark fragmentation’. We calculate the production properties of the tetraquark family Tcss and Tcs¯s at LHC energy for the forthcoming LHC measurements.

Open heavy flavour production in small systems with ALICE

Charm and beauty production measurements in proton–proton (pp) collisions are an important test of perturbative QCD calculations, based on the factorisation approach, which assumes universal fragmentation functions among different collision systems. Recent measurements of charm baryon production at midrapidity in small systems show a baryon-to-meson ratio significanlty higher than that in e+e− and e−p collisions: this observation suggests that charm fragmentation is not universal across different collision systems. Therefore, measurements of charm baryon production are fundamental to characterise the charm quark hadronisation in pp and proton–lead (p–Pb) collisions at the LHC energies. In these proceedings, the latest measurements of D0, D+ and Ds+ mesons, the new measurements of Λc+, Ξc0,+, Σc0,++, the first measurement of Ωc0 baryons and of the non-prompt Λc+, performed with the ALICE detector at midrapidity in pp collisions at s=5.02 and s=13TeV are presented. Furthermore, the recent Λc+/D0 yield ratio, measured down to pT=0 in pp and p–Pb collisions will be discussed together with the measurements of the charm fragmentation fractions into hadrons in pp and p–Pb collisions at sNN=5.02TeV. This rich set of experimental results challenges existing theoretical calculations.

Unifying baryogenesis with dark matter production

We here propose a mechanism that predicts, at early times, both baryon asymmetry and dark matter origin and that recovers the spontaneous baryogenesis during the reheating. Working with U(1)-invariant quark Q and lepton L effective fields, with an interacting term that couples the evolution of Universe’s environment field $$\psi $$ , we require a spontaneous symmetry breaking and get a pseudo Nambu–Goldstone boson $$\theta $$ . The pseudo Nambu–Goldstone boson speeds the Universe up during inflation, playing the role of inflaton, enabling baryogenesis to occur. Thus, in a quasi-static approximation over $$\psi $$ , we impressively find both baryon and dark matter quasi-particle production rates, unifying de facto the two scenarios. Moreover, we outline particle mixing and demonstrate dark matter takes over baryons. Presupposing that $$\theta $$ field energy density dominates as baryogenesis stops and employing recent limits on reheating temperature, we get numerical bounds over dark matter constituent, showing that the most likely dark matter would be consistent with MeV-scale mass candidates. Finally, we briefly underline our predictions are suitable to explain the the low-energy electron recoil event excess between 1 and 7 keV found by the XENON1T collaboration.

High energy sphalerons for baryogenesis at low temperatures

We discuss baryogenesis in scenarios where the Universe is reheated to temperatures $\lesssim 100\,$GeV by the decay of long-lived massive particles into energetic SM particles. Before its thermalization, the center-of-mass energy in collisions between such a particle and a particle from the ambient plasma can be higher than the typical sphaleron mass, even if the temperature of the plasma itself is much lower. Optimistic estimates for the high energy enhancement of the sphaleron cross section suggest that successful baryogenesis is possible for reheating temperatures as low as $0.1\text{-}1\,$GeV. With a simple extension of the SM, sufficient baryon production can be achieved even if more pessimistic results for the sphaleron rate are correct. In both cases this scenario can be probed in collider and cosmic-ray experiments. We briefly discuss the possible origin of the required CP violation.

Heavy-flavor meson and baryon production in high-energy nucleus-nucleus collisions

We present a new model for the description of heavy-flavor hadronization in relativistic heavy-ion collisions. We explore its effect on the charmed hadron yields and kinematic distributions once the latter is applied at the end of transport calculations used to simulate the propagation of heavy quarks in the deconfined fireball produced in the collision. The model is based on the formation of color-singlet clusters through the recombination of charm quarks with light antiquarks or diquarks from the same fluid cell. This local mechanism of color neutralization leads to a strong space-momentum correlation, which provides a substantial enhancement of charmed baryon production and of the collective flow of all charmed hadrons.

High Energy Proton-Proton Interactions and Baryonium Dark Matter

The positive hyperon production asymmetries that have been measured at LHC are real demonstrations of string junction role in the baryon charge transfer at baryon production in HE proton-proton interactions. In order to invent the neutral heavy particle with zero baryon charge as a candidate for Dark Matter, it is necessary to turn back to the times of dual topological unitarization of hadroproduction physics, where the pomeron exchanges play leading role with the growing energies. The topological presentation of pomeron exchange at the HE proton-proton collision is a cylinder that is covered with a quark-gluon net. Taking into account that the junction of three gluons (SJ) has the positive baryon number, as well as the antijunction (antiSJ) is of negative baryon charge, the neutral self-connected baryonium configuration with zero baryon charge is a torus that is covered by a discrete number of hexagons with 3 string junction and 3 antijunction vertices each. The possibilities to observ such baryonium tori are discussed in this paper for three cases: collisions at p-p collider, the cosmic particle collisions with the atmosphere, and in the relativistic jets at the Active Galaxy Nuclei as well.

Production of single-charmed baryons in a quark model approach

The production of single-charmed baryons $\Lambda_c^+ \Lambda_c^-$, $\Lambda_c^+ \Sigma_c^-$+h.c. and $\Sigma_c^+ \Sigma_c^-$ in $p\bar p$ collisions is studied in the framework of a constituent quark model which has satisfactorily described the $N\bar N$ system and the strangeness production $p\bar p\to \Lambda\bar \Lambda$, $\Lambda\bar\Sigma$ and $\Sigma\bar\Sigma$ processes. Predictions on the total cross sections are analyzed for different approaches to the underlying $n\bar n\to c\bar c$ process, mediated by one gluon annihilation diagrams. The results indicate that the cross section is of the order of $1$ nb between $10-14$ GeV for $\Lambda_c^+\Lambda_c^-$ and $\Lambda_c^+ \Sigma_c^-$ channels, and around $0.01-0.1$ nb for $\Sigma_c^+\Sigma_c^-$. This estimations can be relevant for their future search in facilities like $\bar{P}$ANDA.

Track and vertex reconstruction using moving emulsion blocks and a silicon pixel tracker for particles induced by 400 GeV/c protons on a thick target

The SHiP-charm experiment is designed to measure the charm production cross section, including cascade production, of 400 GeV/c protons hitting a thick, SHiP-like target. For the detection of production and decay of heavy charmed particles, emulsion films are employed in a multilayered moving target, forming an emulsion cloud chamber. While the emulsion films provide excellent spatial resolution they do not provide timing information, integrate all events, and quickly get saturated. For the charm measurement the emulsion target is thus moving at a constant speed during data-taking. A first optimization run at the CERN SPS has been performed in 2018, with the purpose to develop the required analysis tools and to fine-tune the detector layout. We report on the experiment design, track reconstruction in the pixel tracker and the track matching with the moving emulsion detector.

Heavy flavour production in pp collisions at LHCb

These proceedings summarise the recent heavy flavour production measurements in proton-proton (pp) collisions at the LHCb experiment. The production cross-sections of J/ψ mesons are measured at a centre-of-mass energy of s=5TeV. The ratio of the Bs0 and B0 fragmentation fractions, fs/fd, is obtained from the combined analysis of different B-decay channels measured by the LHCb experiment. The asymmetry between Λb0 and Λ¯b0 baryon production rates is measured at s=7 and 8TeV.

Pion Productions with Isospin-Dependent In-Medium Cross Sections

Total pion yields and π−/π+ ratios in two Sn+Sn collision systems, 132Sn+124Sn (neutron rich) and 108Sn+112Sn (neutron poor) at E=270A MeV, are significant observables in SAMURAI Pion-Reconstruction and Ion-Tracker (SπRIT) experiments. Based on a recently developed transport model, DaeJeon Boltzmann–Uehling–Uhlenbeck (DJBUU), we investigate the isospin-dependent inmedium effects by including density- and isospin-dependent cross sections for Δ baryon productions. We compare our results with the SπRIT data by considering these effects. We find that the yields as well as the ratios strongly depend on the in-medium effect, especially isospin-dependent in-medium cross sections for Δ resonances.

Fragmentation functions for [formula omitted] using neural networks

We present a determination of fragmentation functions (FFs) for the octet baryon Ξ−/Ξ¯+ from data for single inclusive electron-positron annihilation. Our parametrization in this QCD analysis is provided in terms of a Neural Network (NN). We determine fragmentation functions for Ξ−/Ξ¯+ at next-to-leading order and for the first time at next-to-next-to-leading order in perturbative QCD. We discuss the improvement of higher-order QCD corrections, the quality of fit, and the comparison of our theoretical results with the fitted datasets. As an application of our new set of fragmentation functions, named SHKS22, we present predictions for Ξ−/Ξ¯+ baryon production in proton-proton collisions at the LHC experiments.

High Speed Data Acquisition

A general introduction to high speed data acquisition system techniques in modern particle physics experiments is given. Examples are drawn from the SELEX(E78 1) high statistics charmed baryon production and decay experiment now taking data at Fermilab.

Quantized fragmentation of three-dimensional QCD string

Recent developments of the model of quantized helical QCD string are presented, notably the baryon production. An overview of the experimental evidence is discussed as well as possible applications.

Searches for Heavy Resonances with Substructure

In the past decade, the Large Hadron Collider (LHC) has probed a higher energy scale than ever before. Most models of physics beyond the standard model (BSM) predict the production of new heavy particles; the LHC results have excluded lower masses of such particles. This makes the high-mass regions especially interesting for current and future searches. In most BSM scenarios of interest, the new heavy resonances decay to standard model particles. In a subset of these models, the new particles have large couplings to the top quark, the W and Z bosons, or the Higgs boson. The top quark and W, Z, and Higgs bosons often decay to quarks, giving rise to jets of particles with substructure; event selection based on substructure is used to suppress standard model backgrounds. This review covers the key concepts in experimental searches based on the jet substructure and discusses recent results from the ATLAS and CMS experiments.