Baryon Production Research Articles

Prompt atmospheric neutrinos in the quark\u2013gluon string model

We calculate the atmospheric flux of prompt neutrinos, produced in decays of the charmed particles at energies beyond 1 TeV. Cross sections of the D mesons and {Lambda }^{+}_{c} baryons production in pA and pi A collisions are calculated in the phenomenological quark–gluon string model (QGSM) which is updated using recent measurements of cross sections of the charmed meson production in the LHC experiments. A new estimate of the prompt atmospheric neutrino flux is obtained and compared with the limit from the IceCube experiment, and with predictions of other charm production models.

Studying baryon production using two-particle angular correlations

Latest measurements of ΔηΔφ correlations of identified particles show differences in particle production between baryons and mesons. The correlation functions for mesons exhibit the expected peak dominated by effects of mini-jet fragmentation and are reproduced well by general purpose Monte Carlo generators. For baryon pairs (where both particles have the same baryon number) a surprising near-side anti-correlation structure is observed instead of a peak, implying that two such particles are rarely produced with similar momentum. These results present a challenge to the contemporary models and there is no definite theoretical explanation of the observation. In this proceedings an overview of the latest baryon correlation measurements yielding startling results are presented.

Measurement of production in pp collisions at TeV * * Supported by CERN and national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); MOST and NSFC (China); CNRS/IN2P3 (France); BMBF, DFG and MPG (Germany); INFN (Italy); NWO (Netherlands); MNiSW and NCN (Poland); MEN/IFA (Romania); MSHE (Russia); MinECo (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); DOE NP and NSF

The production of baryons in proton-proton collisions at a centre-of-mass energy of is measured in the transverse-momentum range and the rapidity range . The data used in this measurement correspond to an integrated luminosity of , recorded by the LHCb experiment during 2016. The ratio of the production cross-section times the branching fraction of the decay relative to the prompt production cross-section is found to be , assuming the central value of the measured lifetime, where the first uncertainty is statistical and the second systematic.

Higher N -point function data analysis techniques for heavy particle production and WMAP results

We explore data analysis techniques for signatures from heavy particle production during inflation. Heavy particules can be produced by time dependent masses and couplings, which are ubiquitous in string theory. These localized excitations induce curvature perturbations with non-zero correlation functions at all orders. In particular, Flauger et. al. 2016 has shown that the signal-to-noise as a function of the order $N$ of the correlation function can peak for $N$ of order $\mathcal{O}(1)$ to $\mathcal{O}(100)$ for an interesting space of models. As previous non-Gaussianity analyses have focused on $N=\{3,4\}$, in principle this provides an unexplored data analysis window with new discovery potential. We derive estimators for arbitrary $N$-point functions in this model and discuss their properties and covariances. To lowest order, the heavy particle production phenomenology reduces to a classical Poisson process, which can be implemented as a search for spherically symmetric profiles in the curvature perturbations. We explicitly show how to recover this result from the $N$-point functions and their estimators. Our focus in this paper is on method development, but we provide an initial data analysis using WMAP data, which illustrates the particularities of higher $N$-point function searches.

Higgs as heavy-lifted physics during inflation

Signals of heavy particle production during inflation are encoded as nonanalytic momentum scaling in primordial non-Gaussianity. These non-analytic signatures can be sourced by Standard Model particles with a modified Higgs scale uplifted by the slow-roll dynamics of inflation. We show that such a lifting mechanism becomes more efficient with the presence of a strong Higgs-inflaton mixing, where the Higgs mass scale is further increased by a small speed of sound in the effective theory of inflation. As a primary step towards detecting new particles in the cosmological collider program, non-Gaussianity due to heavy Higgs production in the strong-mixing regime can act as important background signals to be tested by future cosmological surveys.

The atmospheric neutrino flux from decays of charmed particles

We calculate the high-energy component of the atmospheric neutrino flux which arises from decays of the charmed particles. Cross sections of the D mesons and baryons production in pA and πA collisions are calculated within the framework of the quark-gluon string model (QGSM). The recent data on the cross sections of charmed meson production at high energies, obtained in experiments at the LHC, allow an improvement of the QGSM free parameters and new estimate of the prompt atmospheric neutrino flux. The newly-calculated flux of the prompt neutrinos is three times smaller than the flux predicted with the previous version of QGSM. We compare our result with the constraint derived from IceCube experiment as well as with predictions obtained with different charm production models.

Color Randomization of Fast Gluon-Gluon Pairs in the Quark-Gluon Plasma

We study the color randomization of two-gluon states produced after splitting of a primary fast gluon in the quark-gluon plasma. We find that for the LHC conditions the color randomization of the $gg$ pairs is rather slow. At jet energies $E=100$ and $500$ GeV, for typical jet path length in the plasma in central Pb+Pb collisions, the $SU(3)$-multiplet averaged color Casimir of the $gg$ pair differs considerably from its value $2N_c$ for a fully randomized $gg$ state. Our calculations of the energy dependence for generation of the nearly collinear decuplet $gg$ states, that can lead to the baryon jet fragmentation, show that the contribution of the anomalous decuplet color states to the baryon production should become small at $p_T\gtrsim 10$ GeV.

Non-strange and strange D-meson and charm-baryon production in heavy-ion collisions measured with ALICE at the LHC

We present recent results on strange and non-strange D-meson production measured with ALICE in Pb–Pb collisions at the LHC. In addition, the measurements of the Λc+-baryon production and of the Λc+/D0 ratio in pp, p–Pb, and, for the first time ever, Pb–Pb collisions are reported.

Multiplicity dependence of strangeness and hadronic resonance production in pp and p-Pb collisions with ALICE at the LHC

One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p–Pb collisions at sNN=7 and 5.02 TeV, respectively. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has been observed in such systems. We report the latest results on multiplicity dependence of strange and multi-strange hadron production in pp collisions at s=13TeV with ALICE. We also presented recent measurements of mesonic and baryonic resonances in small collision systems like pp and p–Pb at sNN=13 and 8.16 TeV, respectively. The multiplicity dependent studies in pp and p-Pb collisions have been used to investigate how the hadronic scattering processes affect measured resonance yields and to better understand the interplay between canonical suppression and strangeness enhancement. The measurement of the ϕ(1020) meson as a function of multiplicity provides crucial constraints in this context.

Reheating in quintessential inflation via gravitational production of heavy massive particles: a detailed analysis

An improved version of the well-known Peebles-Vilenkin model unifying early inflationary era to current cosmic acceleration, is introduced in order to match with the theoretical values of the spectral quantities provided by it with the recent observational data about the early universe. Since the model presents a sudden phase transition, we consider the simplest way to reheat the universe—via the gravitational production of heavy massive particles—which assuming that inflation starts at GUT scales ∼ 1016 GeV, allows us to use the Wentzel-Kramers-Brillouin (WKB) approximation and consequently this enables us to perform all the calculations in an analytic way. Our results show that the model leads to a maximum temperature at the TeV regime, and passes the bounds to ensure the success of the Big Bang Nucleosynthesis. Finally, we have constrained the quintessence piece of the proposed improved version of the Peebles-Vilenkin model using various astronomical datasets available at present.

New vistas in charm production

We discuss some new aspects of charm production trigerred by recent observations of the LHCb collaboration. The LHCb collaboration measured small asymmetries in production of D+D−mesons as well as $ D_s^ + D_s^ - $ mesons. Is this related to initial quark/antiquark asymmetries in the proton ? Here we discuss a scenario in which unfavored fragmentations $ q/\bar {q} \to D $ and $ s/\bar {s} \to D_s $ are responsible for the asymmetries. We fix the strength of such fragmentations – transition probabilities, by adjusting to the size of the LHCb asymmetries. This has consequences for production of D mesons in forward directions (large xF ) as well as at low energies. Large asymmetries are predicted then in these regions. We present here some of our predictions. Consequences for high-energy neutrino production in the atmosphere are discussed and quantified. The production of Λc baryon at the LHC is disussed. Large deviations from the independent-parton fragmentation picture are found.

Recent results from the cosmic ray program of the NA61/SHINE experiment

NA61/SHINE is a fixed target experiment designed to study hadron-proton, hadron-nucleus and nucleus-nucleus interactions at the CERN Super-Proton-Synchrotron. In this paper we summarize the results from pion-carbon collisions recorded at beam momenta of 158 and 350 GeV=c. Hadron production measurements in these types of interactions is of fundamental importance for the understanding of the muon production in extensive air showers. In particular, production of (anti)baryons and ρ0 are mechanisms responsible for increasing the number of muons which reach the ground. The underestimation of the (anti)baryons or ρ0 production rates in current hadronic interaction models could be one of the sources of the excess of muons observed by cosmic ray experiments. The results on the production spectra of π±, K±, p, ¯p, Λ , ¯Λ, K0S, ρ0, ω and K*0 are presented, as well as their comparison to predictions of hadronic interaction models currently used in air shower simulations.

Mass-dependent cuts in longitudinal phase space

Longitudinal phase space analyses as introduced by van Hove provided a simplified method of separating different reaction production mechanisms. Cuts in the longitudinal phase space can help to select specific reaction kinematics but also induce nonflat acceptance effects in angular distributions. We show that in photoproduction reactions dominated by t-channel exchanges, selection of meson or baryon production over a large mass range can be optimized through calculating mass-dependent cut limits compared to cuts on a van Hove plot sector alone. A cut is presented that improves this selection of one type of hadron production by rejecting another. In addition we demonstrate that using cuts in longitudinal phase space preserves sufficient information to reliably extract observables from the angular distribution of the final state particles.

Investigation the potential of Boron neutron capture therapy (BNCT) to treat the lung cancer

Introduction: Boron neutron capture therapy (BNCT) is recommended to treat the glioblastoma tumor. It is well known that neuron beams are more effective treatment than photon beams to treat hypoxia tumors due to interaction of neutron with nucleus and production of heavy particles such as 7Li and alpha particle. In this study to evaluate the suitability of BNCT for treating of lung cancer, the dose distributions of neutron beam were calculated in lung tumor volume and in peripheral organs at risk (OARs). Materials and Methods: Dose distribution in Boron neutron capture therapy to treat lung cancer was calculated by MCNPX (2.6.0) code. A 3×3×3 cm3 tumor was located in left lung of ORNL phantom and was irradiated with a rectangular field of neutron positioned at surface source distance (SSD) of 10 cm. recommended spectrum of MIT (Massachusetts Institute of Technology) was used. Tumor was loaded with different concentrations of Boron 0, 10, 30 and 60 ppm. Dose delivered to OARs such as heart, spinal cord, right lung … were calculated. Results: The results show that neutron flux significantly decreased followed to penetrate in lung tissue. Neutron flux decreased in all energy bins of irradiated MIT spectrum; maximum fall- off occurred in the range of epithermal energy. Dose distribution was not depended to SSD. The absorbed dose in tumor was 2.16×10-14, 2.6×10-14, 3.44×10-14 and 4.72×10-14 Gy(per one irradiated neutron from source) for boron concentration of 0, 10, 30 and 60 ppm, respectively. From the OARs, the heart tissue absorbed the maximum dose of 1.66×10-15 Gy (per one irradiated neutron from source). Conclusion: Our simulated model was successful to calculated organ doses in BNCT. As the boron concentration in lung tumor increases, absorbed dose increased while dose uniformity trended downward. Our results show that the MIT neutron source is suitable to treat deep lung tumors while OVRs’ dose maintains within the threshold dose.

Influence of anisotropic Λ/Σ creation on the Ξ− multiplicity in subthreshold proton–nucleus collisions

We present an analysis of Ξ− baryon production in subthreshold proton–nucleus (p+A) collisions in the framework of a BUU type transport model. We propose a new mechanism for Ξ production in the collision of a secondary Λ or Σ hyperon and a nucleon from the target nucleus. We find that the Ξ− multiplicity in p+A collisions is sensitive to the angular distribution of hyperon production in the primary N+N collision. Using reasonable assumptions on the unknown elementary cross sections we are able to reproduce the Ξ− multiplicity and the Ξ−/(Λ+Σ0) ratio obtained in the HADES experiment in p+Nb collisions at sNN= 3.2 GeV energy.

First measurement of Ξ− polarization in photoproduction

Despite decades of studies of the photoproduction of hyperons, both their production mechanisms and their spectra of excited states are still largely unknown. While the parity-violating weak decay of hyperons offers a means of measuring their polarization, which could help discern their production mechanisms and identify their excitation spectra, no such study has been possible for doubly strange baryons in photoproduction, due to low production cross sections. However, by making use of the reaction γp→K+K+Ξ−, we have measured, for the first time, the induced polarization, P, and the transferred polarization from circularly polarized real photons, characterized by Cx and Cz, to recoiling Ξ−s. The data were obtained using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab for photon energies from just over threshold (2.4 GeV) to 5.45 GeV. These first-time measurements are compared, and are shown to broadly agree, with model predictions in which cascade photoproduction proceeds through the decay of intermediate hyperon resonances that are produced via relativistic meson exchange, offering a new step forward in the understanding of the production and polarization of doubly-strange baryons.

-baryon production in pp collisions in the general-mass variable-flavour-number scheme, and comparison with CMS and LHCb data

We calculate the next-to-leading-order cross section for the inclusive production of Λb baryons in pp collisions in the general-mass variable-flavor-number scheme. We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in e+e− annihilation and compare our results for transverse-momentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC. We find satisfactory agreement in general, with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.

Production of single-charm hadrons by the quark-combination mechanism in p -Pb collisions at sNN=5.02 TeV

If QGP-like medium is created in $p$-Pb collisions at extremely high collision energies, charm quarks that move in the medium can hadronize by capturing the co-moving light quark(s) or anti-quark(s) to form the charm hadrons. Using light quark $p_{T}$ spectra extracted from the experimental data of light-flavor hadrons and a charm quark $p_{T}$ spectrum that is consistent with perturbative QCD calculations, the central-rapidity data of $p_{T}$ spectra and the spectrum ratios for $D$ mesons in the low $p_{T}$ range ($p_{T}\lesssim7$ GeV/$c$) in minimum-bias $p$-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV are well described by quark combination mechanism in equal-velocity combination approximation. The $\Lambda_{c}^{+}/D^{0}$ ratio in quark combination mechanism exhibits the typical increase-peak-decrease behavior as the function of $p_{T}$, and the shape of the ratio for $p_{T}\gtrsim3$ GeV/$c$ is in agreement with the data of ALICE collaboration in central rapidity region $-0.96<y<0.04$ and the preliminary data of LHCb collaboration in forward rapidity region $1.5<y<4.0$. The global production of single-charm baryons is quantified using the data and the possible enhancement (relative to light flavor baryons) is discussed. The $p_{T}$ spectra of $\Xi_{c}^{0}$, $\Omega_{c}^{0}$ in minimum-bias events and those of single-charm hadrons in high-multiplicity event classes are predicted, which serves as the further test of the possible change of the hadronization characteristic for low $p_{T}$ charm quarks in the small system created in $p$-Pb collisions at LHC energies.

Doubly charmed baryon production in heavy ion collisions

We give an estimate of $\Xi_{cc}^{++}$ production rate and transverse momentum spectra in relativistic heavy ion collisions. We use Boltzmann transport equations to describe the dynamical evolution of charm quarks and diquarks inside quark-gluon plasma. In-medium formation and dissociation rates of charm diquarks are calculated from potential non-relativistic QCD for the diquark sector. We solve the transport equations by Monte Carlo simulations. For $2.76$ TeV Pb-Pb collisions with $0-10\%$ centrality, the number of $\Xi_{cc}^{++}$ produced in the transverse momentum range $0-5$ GeV and rapidity from $-1$ to $1$ is roughly $0.02$ per collision. We repeat the calculation with a melting temperature $250$ MeV above which no diquarks can be formed. The number of $\Xi_{cc}^{++}$ produced in the same kinematic region is about $0.0125$ per collision. We discuss how to study diquarks at finite temperature on a lattice and construct the anti-triplet free energy in a gauge invariant but path dependent way. We also comment on extensions of the calculation to other doubly heavy baryons and doubly heavy tetraquarks and the feasibility of experimental measurements.

\u039bc+ production in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV

The pT-differential production cross section of prompt Λc+ charmed baryons was measured with the ALICE detector at the Large Hadron Collider (LHC) in pp collisions at sqrt{s}=7 TeV and in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV at midrapidity. The Λc+ and {overline{varLambda}}_{overline{mathrm{c}}} were reconstructed in the hadronic decay modes Λc+ → pK−π+, Λc+ → pKS0 and in the semileptonic channel Λc+ → e+νeΛ (and charge conjugates). The measured values of the Λc+/D0 ratio, which is sensitive to the c-quark hadronisation mechanism, and in particular to the production of baryons, are presented and are larger than those measured previously in different colliding systems, centre-of-mass energies, rapidity and pT intervals, where the Λc+ production process may differ. The results are compared with the expectations obtained from perturbative Quantum Chromodynamics calculations and Monte Carlo event generators. Neither perturbative QCD calculations nor Monte Carlo models reproduce the data, indicating that the fragmentation of heavy-flavour baryons is not well understood. The first measurement at the LHC of the Λc+ nuclear modification factor, RpPb, is also presented. The RpPb is found to be consistent with unity and with that of D mesons within the uncertainties, and consistent with a theoretical calculation that includes cold nuclear matter effects and a calculation that includes charm quark interactions with a deconfined medium.