Production Cross Section Research Articles

Search for production of a single vectorlike quark decaying to tH or tZ in the all-hadronic final state in pp collisions at s=13 TeV

A search for electroweak production of a single vectorlike T quark in association with a bottom (b) quark in the all-hadronic decay channel is presented. This search uses proton-proton collision data at s=13 TeV collected by the CMS experiment at the CERN LHC during 2016–2018, corresponding to an integrated luminosity of 138 fb−1. The T quark is assumed to have charge 2/3 and decay to a top (t) quark and a Higgs (H) or Z boson. Hadronic decays of the t quark and the H or Z boson are reconstructed from the kinematic properties of jets, including those containing b hadrons. No deviation from the standard model prediction is observed in the reconstructed tH and tZ invariant mass distributions. The 95% confidence level upper limits on the product of the production cross section and branching fraction of a T quark produced in association with a b quark and decaying via tH or tZ range from 1260 to 68 fb for T quark masses of 600–1200 GeV. © 2024 CERN, for the CMS Collaboration 2024 CERN

Prompt gamma rays of lanthanum and praseodymium produced by inelastic scattering of fission neutrons

AbstractEmission of prompt gamma rays in lanthanum and praseodymium nuclei triggered by (n,n’γ) inelastic scattering reactions of fission neutrons was investigated with the instrument FaNGaS (Fast Neutron-induced Gamma-ray Spectrometry) at Heinz Maier-Leibnitz Zentrum (MLZ). We identified 125 gamma lines (54 for lanthanum and 71 for praseodymium), for which we give the relative intensities and production cross sections. Presence of oxygen and chlorine in the samples was exploited to verify previous measurements. Our results are consistent with available literature data but also enhance it as we detect new lines and recognize a few false assignments. In addition, for a counting time of 12 h we estimated the detection limits of lanthanum and praseodymium as 0.6 and 0.4 mg, respectively.

Effective field theory descriptions of Higgs boson pair production

Higgs boson pair production is traditionally considered to be of particular interest for a measurement of the trilinear Higgs self-coupling. Yet it can offer insights into other couplings as well, since – in an effective field theory (EFT) parameterisation of potential new physics – both the production cross section and kinematical properties of the Higgs boson pair depend on various other Wilson coefficients of EFT operators. This note summarises the ongoing efforts related to the development of EFT tools for Higgs boson pair production in gluon fusion, and provides recommendations for the use of distinct EFT parameterisations in the Higgs boson pair production process. This document also outlines where further efforts are needed and provides a detailed analysis of theoretical uncertainties. Additionally, benchmark scenarios are updated. We also re-derive a parameterisation of the next-to-leading order (NLO) QCD corrections in terms of the EFT Wilson coefficients both for the total cross section and the distribution in the invariant mass of the Higgs boson pair, providing for the first time also the covariance matrix. A reweighting procedure making use of the newly derived coefficients is validated, which can be used to significantly speed up experimental analyses.

Search for a new Z′ gauge boson via the pp→W±(*)→Z′μ±ν→μ±μ∓μ±ν process in pp collisions at s=13 TeV with the ATLAS detector

A search for a new Z′ gauge boson predicted by Lμ−Lτ models, based on charged-current Drell–Yan production, pp→W±(*)→Z′μ±ν→μ±μ∓μ±ν, is presented. The data sample used corresponds to an integrated luminosity of 140 fb−1 of proton–proton collisions at s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The search examines a final state of 3μ plus large missing transverse momentum. Upper limits are set on the Z′ production cross section times branching ratio in the mass range of 5–81 GeV. After combining with the previous Z′ search using the neutral-current Drell–Yan production with a 4μ final state, the most stringent exclusion limits to date are achieved in the parameter space of the Z′ coupling strength and mass. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Probing hidden leptonic scalar portals using the NA64 experiment at CERN

In this study, we demonstrate the potential of the NA64 experiment at CERN SPS to search for New Physics processes involving e→μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$e\\rightarrow \\mu $$\\end{document} transitions after the collision of 100 GeV electrons with target nuclei. A new Dark Sector leptonic portal in which a scalar boson φ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\varphi $$\\end{document} could be produced in the lepton-flavor-changing bremsstrahlung-like reaction, eN→μNφ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$eN\\rightarrow \\mu N\\varphi $$\\end{document}, is used as benchmark process. In this work, we develop a realistic Monte Carlo simulation of the NA64 experimental setup implementing the differential and total production cross-section computed at exact tree-level and applying the Weiszäcker–Williams phase space approximation. Using this framework, we investigate the main background sources and calculate the expected sensitivity of the experiment. The results indicate that with minor setup optimization, NA64 can probe a large fraction of the available parameter space compatible with the muon g-2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$g-2$$\\end{document} anomaly and the Dark Matter relic predictions in the context of a new Dark Sector leptonic portal with 1011\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{11}$$\\end{document} EOT. This result paves the way to the exploration of lepton-flavour-changing transitions in NA64.

Alpha-particles induced reactions on natZr as a pathway of medical 90Nb production

Reactions on natZr induced by alpha-particles with energies up to 60 MeV were studied by stacked foils method. Production cross-sections for zirconium (88,89,95Zr), niobium (90,92m,95m,95,96Nb) and molybdenum (90,93m,99Mo) radionuclides were determined and thick target yields were calculated. The possibility of obtaining 90Nb through the intermediate formation of 90Mo is discussed. It is possible to obtain 19.6 MBq/(μA·h) 90Mo upon saturation, that leads to 4 MBq/(μA·h) 90Nb after decay.

Search for Higgs boson pair production with one associated vector boson in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV

A search for Higgs boson pair (HH) production in association with a vector boson V (W or Z boson) is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV, collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb−1. Both hadronic and leptonic decays of V bosons are used. The leptons considered are electrons, muons, and neutrinos. The HH production is searched for in the bb¯bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ extrm{b}\\overline{\ extrm{b}}\ extrm{b}\\overline{\ extrm{b}} $$\\end{document} decay channel. An observed (expected) upper limit at 95% confidence level of VHH production cross section is set at 294 (124) times the standard model prediction. Constraints are also set on the modifiers of the Higgs boson trilinear self-coupling, kλ, assuming k2V = 1, and vice versa on the coupling of two Higgs bosons with two vector bosons, k2V. The observed (expected) 95% confidence intervals of these coupling modifiers are −37.7 < kλ < 37.2 (−30.1 < kλ < 28.9) and −12.2 < k2V < 13.5 (−7.2 < k2V < 8.9), respectively.

Determination of the Relative Sign of the Higgs Boson Couplings to W and Z Bosons Using WH Production via Vector-Boson Fusion with the ATLAS Detector.

The associated production of Higgs and W bosons via vector-boson fusion is highly sensitive to the relative sign of the Higgs boson couplings to W and Z bosons. In this Letter, two searches for this process are presented, using 140 fb^{-1} of proton-proton collision data at sqrt[s]=13 TeV recorded by the ATLAS detector at the LHC. The first search targets scenarios with opposite-sign couplings of the W and Z bosons to the Higgs boson, while the second targets standard model-like scenarios with same-sign couplings. Both analyses consider Higgs boson decays into a pair of b quarks and W boson decays with an electron or muon. The data exclude the opposite-sign coupling hypothesis with a significance beyond 5σ, and the observed (expected) upper limit set on the cross section for vector-boson fusion WH production is 9.0 (8.7) times the standard model value at 95% confidence level.

Production cross sections of 102mRh and 108mAg in proton bombed natPb target with 400 MeV energy

The accelerator-driven subcritical system (ADS) is a competitive option for next-generation nuclear energy systems. Production cross sections of long-lived residual radioactive nuclides in a proton-nuclide reaction are basic quantities for the calculation of accumulated radioactivity in the use of ADS systems. This work presents the production cross sections of 102mRh and 108mAg in a natural lead (natPb) target activated by 400 MeV protons. The natPb target was irradiated by a 400 MeV proton beam in NRC “Kurchatov Institute” and measured two decades later by a low background gamma spectrometer in China Jinping Underground Laboratory (CJPL). A spectrum analysis method based on simulated single-isotope spectrum and Bayesian peak fitting was employed to compute the activities and production cross sections of the residual nuclides. The experimentally measured cross-sections for 102mRh and 108mAg were 0.72 ± 0.05 mb and 0.76 ± 0.09 mb respectively. These values are approximately twice as high as those predicted by the QGSP_INCLXX_HP model and fall within the range predicted by the INCL4+ABLA and LAQGSM+GEM2 models for mass numbers A=102 and A=108. These findings offer new experimental insights for ADS research and provide a practical benchmark for theoretical models concerning proton-lead interactions.

Combined explanation of LHC multilepton, diphoton, and top-quark excesses

In this article, we propose the Δ2HDMS as a combined explanation of several excesses and anomalies observed at the LHC. Especially, tt¯ differential distributions point towards the associated production of new electroweak scale Higgs bosons decaying into bottom quarks and W bosons (&gt;5σ) with masses consistent with the diphoton excesses at ≈95 GeV and ≈151.5 GeV (3.8σ and 4.9σ, respectively). Furthermore, CMS found indications for resonant tt¯ production at ≈400 GeV (3.5σ) and both ATLAS and CMS reported elevated four-top and tt¯W cross sections. The Δ2HDMS is obtained by supplementing the SM Higgs (H2) with a second scalar doublet (H1), real scalar singlet (S), and a Higgs triplet with zero hypercharge (Δ). We fix the masses of the neutral tripletlike and the singletlike scalars by the diphoton excesses, i.e., mΔ0=151.5 GeV and mS=95 GeV, respectively. H, the CP-even component of H1, is produced via gluon fusion from a top-loop and decays dominantly to S+Δ0 whose subsequent decays to W+W− and bb¯ explain the differential tt¯ distributions for σ(pp→H→SΔ0)≈5 pb. Choosing the top-Yukawa of H1 accordingly, the CP-odd Higgs boson A turns out to have the right production cross section to account for the resonant tt¯ excess at 400 GeV, while the top-associated production of H and A results in new physics pollution of Standard Model tt¯W and tt¯tt¯ cross sections, as preferred by the data. Published by the American Physical Society 2024

Experimental determination of the sulfur K-shell fundamental parameters employing the holistic approach

Abstract Sulfur and its compounds are both very abundant in the environment and very important for technological applications such as batteries. X-ray spectroscopic characterizations of sulfur compounds for a quantitative determination of the present amount of sulfur often requires a good knowledge on the atomic fundamental parameters involved. These quantitatively describe the processes of photoionization and X-ray fluorescence emission, making them crucial for X-ray spectroscopy-based quantifications. &amp;#xD;By employing the recently demonstrated holistic approach, the atomic fundamental parameters of the sulfur K-shell were experimentally determined using the radiometrically calibrated instrumentation of the Physikalisch-Technische Bundesanstalt (PTB). The transition probabilities of the main K-shell fluorescence lines, the K-shell fluorescence yield, the K-shell Auger yield, the subshell photoionization cross section and fluorescence production cross section were determined by means of photon energy dependent X-ray fluorescence and transmission measurements on a thin InS coated silicon nitride membrane. The results are also downloadable from Zenodo as plain text.

Search for decays of the Higgs boson into a pair of pseudoscalar particles decaying into bb¯τ+τ− using pp collisions at s=13 TeV with the ATLAS detector

This paper presents a search for exotic decays of the Higgs boson into a pair of new pseudoscalar particles, H→aa, where one pseudoscalar decays into a b-quark pair and the other decays into a τ-lepton pair, in the mass range 12≤ma≤60 GeV. The analysis uses pp collision data at s=13 TeV collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb−1. No significant excess above the Standard Model (SM) prediction is observed. Assuming the SM Higgs boson production cross section, the search sets upper limits at 95% confidence level on the branching ratio of Higgs bosons decaying into bb¯τ+τ−, B(H→aa→bb¯τ+τ−), between 2.2% and 3.9% depending on the pseudoscalar mass. © 2024 CERN, for the ATLAS Collaboration 2024 CERN

Prediction of (n, 2n) reaction cross-sections of long-lived fission products based on tensor model

Prediction of (n, 2n) reaction cross-sections of long-lived fission products based on tensor model

Measurements of the production cross-section for a Z boson in association with b- or c-jets in proton–proton collisions at s=13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 13$$\\end{document} TeV with the ATLAS detector

This paper presents a measurement of the production cross-section of a Z boson in association with b- or c-jets, in proton–proton collisions at s=13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sqrt{s} = 13$$\\end{document} TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {fb}^{-1}$$\\end{document}. Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum pT>20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$p_\ ext {T} > 20$$\\end{document} GeV and rapidity |y|<2.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$|y| < 2.5$$\\end{document}. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z+≥1c\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z + \\ge 1~c$$\\end{document}-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions.

Nitrosation mechanisms, kinetics, and dynamics of the guanine and 9-methylguanine radical cations by nitric oxide-Radical-radical combination at different electron configurations.

As a precursor to various reactive nitrogen species formed in biological systems, nitric oxide (•NO) participates in numerous processes, including enhancing DNA radiosensitivity in ionizing radiation-based radiotherapy. Forming guanine radical cations is another common DNA lesion resulting from ionization and oxidation damage. As such, the interaction of •NO with guanine radical cations (G•+) may contribute to the radiosensitization of •NO. An intriguing aspect of this process is the participation of multiple spin configurations in the reaction, including open-shell singlet 1,OS[G•+(↑)⋯(↓)•NO], closed-shell singlet 1,CS[G(↑↓)⋯NO+], and triplet 3[G•+(↑)⋯(↑)•NO]. In this study, the reactions of •NO with both unsubstituted guanine radical cations (in the 9HG•+ conformation) and 9-methylguanine radical cations (9MG•+, a guanosine-mimicking model compound) were investigated in the absence and presence of monohydration of radical cations. Kinetic-energy dependent reaction product ions and cross sections were measured using an electrospray ionization guided-ion beam tandem mass spectrometer. The reaction mechanisms, kinetics, and dynamics were comprehended by interpreting the reaction potential energy surface using spin-projected density functional theory, coupled cluster theory, and multiconfiguration complete active space second-order perturbation theory, followed by RRKM kinetics modeling. The combined experimental and computational findings revealed closed-shell singlet 1,CS[7-NO-9MG]+ as the major, exothermic product and triplet 3[8-NO-9MG]+ as the minor, endothermic product. Singlet biradical products were not detected due to high reaction endothermicities, activation barriers, and inherent instability.

Search for a resonance decaying to a W boson and a photon in proton-proton collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 13 TeV using leptonic W boson decays

A search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb−1. Particle X has electric charge ±1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%).

Deep learning to improve the sensitivity of Di-Higgs searches in the 4b channel

The study of di-Higgs events, both resonant and non-resonant, plays a crucial role in understanding the fundamental interactions of the Higgs boson. In this work we consider di-Higgs events decaying into four b-quarks and propose to improve the experimental sensitivity by utilizing a novel machine learning algorithm known as Symmetry Preserving Attention Network (Spa-Net) — a neural network structure whose architecture is designed to incorporate the inherent symmetries in particle reconstruction tasks. We demonstrate that the Spa-Net can enhance the experimental reach over baseline methods such as the cut-based and the Dense Neural Network-based analyses. At the Large Hadron Collider, with a 14-TeV center-of-mass energy and an integrated luminosity of 300 fb−1, the Spa-Net allows us to establish 95% C.L. upper limits in resonant production cross-sections that are 10% to 45% stronger than baseline methods. For non-resonant di-Higgs production, Spa-Net enables us to constrain the self-coupling that is 9% more stringent than the baseline method.

A study on the synthesis of superheavy element Mc (Z = 115) using lead, bismuth and actinide targets

The evaporation residue cross sections in synthesizing isotopes of superheavy element Mc (Z = 115) by the hot fusion reactions 48Ca+241,243Am→289,291Mc, 45Sc+240,242,244Pu→285,287,289Mc, 50Ti+236,237Np→286,287Mc, 51V+238U→289Mc, 36S+253Es→289Mc, 46K+248Cm→294Mc, and by the cold fusion reactions 78As+208Pb→286Mc, 76Ge+209Bi→285Mc have been systematically investigated using the phenomenological model for production cross section. We have predicted the most effective projectile-target combinations for synthesizing Mc isotopes among these reactions. Our result shows that the 3n- channel cross section is larger for the reaction 48Ca+243Am→291Mc, and the 4n- channel cross section is larger for the reaction 46K+248Cm→294Mc. This study also examines the effect of the use of mass values and shell corrections by the Möller and Warsaw groups. Using our predicted combinations and the cross section values at a range of excitation energies, we hope these isotopes of Mc can be synthesized in near-future experiments.

Systematic study of theoretical estimation of nuclear reaction cross section of proton-induced reactions on Neodymium target upto 65 MeV using TALYS-1.96 code

Abstract Systematic study of theoretical estimation of nuclear cross section of charged particle induced reactions on rare earth nuclei has been carried out. The production cross section of the $^{150,149,148,146,144,143,141}$Pm and $^{149,147}$Nd nuclei were calculated theoretically via proton induced reaction on neodymium using TALYS (version 1.96) code in the default mode, with different combination of nuclear models as well as using adjusted nuclear model parameters from reaction threshold to the proton energy upto 65 MeV. The theoretically computed results were compared with the experimental results taken from EXFOR database and literature, reported by various research groups. Moreover, the effect of the various Level Density Models (LDMs), Preequilibrium Models (PEs), Optical Model Potentials (OMPs), gamma Strength Functions ($\gamma$SFs) in the cross section calculation were taken into consideration. The present theoretical analysis will help to understand the theory of nuclear reaction models and improve the evaluated nuclear data libraries.

Heavy flavor production under a strong magnetic field

The magnetic field created in high energy nuclear collisions will affect the QCD dynamical processes, such as the heavy quark production which happens in the initial stage of the collisions. We calculate in a strong magnetic field the heavy quark production cross section of the process gg→QQ¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ gg\ o Q\\overline{Q} $$\\end{document} at leading order and the corresponding transverse momentum distribution in nucleus-nucleus collisions. In comparison to the QED process, the heavy quark production is dominated by the unique QCD channel with gluon self-interaction. Due to the dimension reduction of quark phase space in a strong magnetic field, the production is concentrated in a very narrow energy region above the threshold. Since the rotational invariance is broken in a magnetic field, the production becomes anisotropic.