Inclusive Production Cross Section Research Articles

Charm Meson Production and Double Parton Interactions at the LHC

We discuss production of open charm mesons in proton-proton collisions at the LHC. The cross section for inclusive production of $c \bar c$ pairs is calculated within the $k_{\perp}$-factorization approach in which a major part of higher-order corrections is belived to be effectively included. We use and test the applicability of several unintegrated gluon distributions. Numerical results of the $k_{\perp}$-factorization approach are compared to NLO pQCD collinear predictions. Inclusive differential distributions in transverse momentum and (pseudo)rapidity of several charmed mesons are presented and compared to recent results of the ALICE, ATLAS and LHCb collaborations. We also examine production of neutral charmed meson-antimeson pairs ($D^0 {\overline D^0}$) in unique kinematics of forward rapidities of the LHCb experiment. Kinematical correlations in azimuthal angle $\varphi_{D^0 {\overline D^0}}$, invariant mass $M_{D^0 {\overline D^0}}$ and rapidity difference $Y_{D^0 {\overline D^0}}$ distributions are calculated. Moreover, we also discuss production of two pairs of $c \bar c$ within a simple formalism of double-parton scattering (DPS). We compare results of calculations of single-parton scattering (SPS) and double-parton scattering (DPS) for production of $c \bar c c \bar c$ and for $D^0-D^0$ meson-meson correlations. We compare our predictions for double charm production with recent results of the LHCb collaboration for azimuthal angle $\varphi_{D^0 D^0}$ distribution, dimeson invariant mass $M_{D^0 D^0}$ and rapidity distance between mesons $Y_{D^0 D^0}$. The obtained results clearly certify the dominance of DPS in the production of events with double charm.

Top quark pair production cross section with the ATLAS experiment

This document reviews the existing results of inclusive top quark pair production cross section measurements in proton-proton collisions at a center of mass energies of 7 and 8 TeV performed with the ATLAS detector at the Large Hadron Collider. These measurements cover the different analysis channels, single lepton, dilepton and all hadronic channel, as well as dedicated analysis for channels including tau leptons decaying hadronically. All measurements shown in this document are in good agreement with the Standard Model expectation.

FRAGMENTATION FUNCTIONS AT BABAR

Inclusive hadron production cross section in e+e- annihilation shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of inclusive spectra of charged pions, kaons, and protons (antiprotons) produced in e+e- collisions at the center-of-mass energy of 10.54 GeV, and tests of QCD predictions and hadronization models. We also report the results on the measurement of the azimuthal modulation induced by the Collins effect in inclusive production of charged pion pairs e+e- → ππX, where the two pions are produced in opposite hemispheres. These data allows the determination of the polarized Collins fragmentation functions.

Recent ATLAS results in the field of meson physics

Recent results on flavor physics are presented, using data from the ATLAS detector. The ϓ(nS ) and charmonium inclusive production cross sections are discussed. J/ψ production associated with a W vector boson is presented. An inclusive analysis of B + meson production is shown. Results on the production of heavy quarkonia are complemented by the measurement of inclusive φ meson production. The latest information on heavy flavor spectroscopy and searches for new physics using B -meson rare decays is also covered. These results are based on data samples collected during the 2011 and 2012 LHC running periods.

Determination of the top-quark pole mass and strong coupling constant from the [formula omitted] production cross section in pp collisions at [formula omitted

The inclusive cross section for top-quark pair production measured by the CMS experiment in proton–proton collisions at a center-of-mass energy of 7 TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, mtpole, or the strong coupling constant, αS. With the parton distribution function set NNPDF2.3, a pole mass of 176.7−3.4+3.8 GeV is obtained when constraining αS at the scale of the Z boson mass, mZ, to the current world average. Alternatively, by constraining mtpole to the latest average from direct mass measurements, a value of αS(mZ)=0.1151−0.0032+0.0033 is extracted. This is the first determination of αS using events from top-quark production.

Search for a new bottomonium state decaying to [formula omitted] in pp collisions at [formula omitted

The results of a search for the bottomonium counterpart, denoted as Xb, of the exotic charmonium state X(3872) is presented. The analysis is based on a sample of pp collisions at s=8 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 20.7 fb−1. The search looks for the exclusive decay channel Xb→ϒ(1S)π+π− followed by ϒ(1S)→μ+μ−. No evidence for an Xb signal is observed. Upper limits are set at the 95% confidence level on the ratio of the inclusive production cross sections times the branching fractions to ϒ(1S)π+π− of the Xb and the ϒ(2S). The upper limits on the ratio are in the range 0.9–5.4% for Xb masses between 10 and 11 GeV. These are the first upper limits on the production of a possible Xb at a hadron collider.

Erratum: Phenomenology of QCD threshold resummation for gluino pair production at NNLL

We examine the impact of threshold resummation for the inclusive hadronic production cross section of gluino pairs at next-to-next-to-leading-logarithmic accuracy, compared to the exact next-to-leading-order cross section and the next-to-next-to-leading-order approximation. Here, we apply formulas derived recently in the classical Mellin-space formalism. Moreover, we give the analytic input for the alternative momentum-space formalism and discuss the crucial points of the numeric implementation. We find that soft resummation keeps the hadronic cross section close to the fixed next-to-leading-order result.

Multiple scattering effects on inclusive particle production in the large-xregime

We study the multiple scattering effects on inclusive particle production in $\mathrm{p}+\mathrm{A}$ and $\ensuremath{\gamma}+\mathrm{A}$ collisions. Specifically, we concentrate on the region where the parton momentum fraction in the nucleus $x\ensuremath{\sim}\mathcal{O}(1)$ and incoherent multiple interactions are relevant. By taking into account both initial-state and final-state double scattering, we derive the nuclear size-enhanced power corrections to the differential cross section for single inclusive hadron production in $\mathrm{p}+\mathrm{A}$ and $\ensuremath{\gamma}+\mathrm{A}$ reactions, and for prompt photon production in $\mathrm{p}+\mathrm{A}$ reactions. We find that the final result can be written in a simple compact form in terms of four-parton correlation functions, in which the second-derivative, first-derivative and nonderivative terms of the correlation distributions share the same hard-scattering functions. We expect our result to be especially relevant for understanding the nuclear modification of particle production in the backward rapidity regions in $\mathrm{p}+\mathrm{A}$ and $\mathrm{e}+\mathrm{A}$ collisions.

Production of charged pions, kaons, and protons ine+e−annihilations into hadrons ats=10.54 GeV

Inclusive production cross sections of $\pi^\pm$, $K^\pm$ and $p\bar{p}$ per hadronic $e^+e^-$ annihilation event in $e^+e^-$ are measured at a center-of-mass energy of 10.54 GeV, using a relatively small sample of very high quality data from the BaBar experiment at the PEP-II $B$-factory at the SLAC National Accelerator Laboratory. The drift chamber and Cherenkov detector provide clean samples of identified $\pi^\pm$, $K^\pm$ and $p\bar{p}$ over a wide range of momenta. Since the center-of-mass energy is below the threshold to produce a $B\bar{B}$ pair, with $B$ a bottom-quark meson, these data represent a pure $e^+e^- \rightarrow q\bar{q}$ sample with four quark flavors, and are used to test QCD predictions and hadronization models. Combined with measurements at other energies, in particular at the $Z^0$ resonance, they also provide precise constraints on the scaling properties of the hadronization process over a wide energy range.

Inclusive b-jet production in heavy ion collisions at the LHC

Theoretical and experimental advances in understanding light jet production and modification in Pb+Pb reactions at sNN=2.76 TeV have been a highlight of the LHC heavy ion program. At the same time, the detailed mechanisms of heavy quark propagation and energy loss in dense QCD matter are not yet fully understood. With this motivation, we present theoretical predictions for the nuclear-induced attenuation of the differential cross section for inclusive b-jet production in heavy ion collisions at the LHC for comparison to upcoming data. We find that for transverse momenta pT≳75 GeV both hadronization and mass effects are negligible and this attenuation is comparable to the one observed for light jets. We discuss how the detailed b-jet quenching patterns can be used to gain new insight into the in-medium heavy flavor dynamics.

Precision Measurement of Charged Pion and Kaon Differential Cross Sections ine+e−Annihilation ats=10.52 GeV

Measurements of inclusive differential cross sections for charged pion and kaon production in e+ e- annihilation have been carried out at a center-of-mass energy of sqrt[s]=10.52 GeV. The measurements were performed with the Belle detector at the KEKB e+ e- collider using a data sample containing 113×10(6) e+ e- → qq events, where q={u,d,s,c}. We present charge-integrated differential cross sections dσ(h±)/dz for h±={π±,K±} as a function of the relative hadron energy z=2E(h)/sqrt[s] from 0.2 to 0.98. The combined statistical and systematic uncertainties for π± (K±) are 4% (4%) at z∼0.6 and 15% (24%) at z∼0.9. The cross sections are the first measurements of the z dependence of pion and kaon production for z>0.7 as well as the first precision cross section measurements at a center-of-mass energy far below the Z0 resonance used by the experiments at LEP and SLC.

Measurement of the single top quark t-channel cross section with a template fit analysis

We present a measurement of the inclusive single top t-channel production cross section in proton-proton collisions at the LHC, using data collected with the CMS experiment during 2011 and 2012. The analyzed data correspond to an integrated luminosity of 1.17/1.56 fb−1 for muon/electron channel respectively at the centre-of-mass energy of 7TeV, and to 5.0 fb−1 at 8 TeV. The analysis exploits the pseudorapidity distribution of the recoil jet and reconstructed top-quark mass using background estimates determined from control samples in data. The measurement is used to determine the CKM matrix element |Vtb|.

Inclusive cross sections for gluon production in collision of two projectiles on two targets in the BFKL approach

Inclusive cross-sections for gluon production in collision of two mucleons with two nucleons are studied in the BFKL approach. Various contributions include emission from the pomerons attached to the participants, from the BFKL interactions in between these pomerons and from the intermediate BKP state. The last contribution may be observable provided the growth with energy of the pomeron contribution is tamed in accordance with unitarity.

Soft-gluon resummation for single-particle inclusive hadroproduction at high transverse momentum

We consider the cross section for one-particle inclusive production at high transverse momentum in hadronic collisions. We present the all-order resummation formula that controls the logarithmically-enhanced perturbative QCD contributions to the partonic cross section in the threshold region, at fixed rapidity of the observed parton (hadron). The explicit resummation up to next-to-leading logarithmic accuracy is supplemented with the computation of the general structure of the near-threshold contributions to the next-to-leading order cross section. This next-to-leading order computation allows us to extract the one-loop hard-virtual amplitude that enters into the resummation formula. This is a necessary ingredient to explicitly extend the soft-gluon resummation beyond the next-to-leading logarithmic accuracy. These results equally apply to both spin-unpolarized and spin-polarized scattering processes.

Phenomenology of QCD threshold resummation for gluino pair production at NNLL

Abstract We examine the impact of threshold resummation for the inclusive hadronic production cross section of gluino pairs at next-to-next-to-leading-logarithmic accuracy, compared to the exact next-to-leading-order cross section and the next-to-next-to-leading-order approximation. Here, we apply formulas derived recently in the classical Mellin-space formalism. Moreover, we give the analytic input for the alternative momentum-space formalism and discuss the crucial points of the numeric implementation. We find that soft resummation keeps the hadronic cross section close to the fixed next-to-leading-order result.

Hadron production measurement from NA61/SHINE

An overview of the recent NA61/SHINE results on determination of charged hadron yields in proton-carbon interactions is presented. The results aim to improve predictions of the neutrino flux in the T2K experiment. The data were recorded using a secondary-proton beam of 31 GeV/c momentum from CERN SPS scattered off a graphite target. To determine the inclusive production cross-section for charged pions, kaons and protons the thin (0.04 λI) target was exploited. Results of this measurement are used in the T2K beam simulation program to reweight hadron yields in the primary interaction vertex and allow to constrain directly about 60% of the neutrino flux. At the same time, NA61/SHINE results obtained with the T2K replica target (1.9 λI) would allow to constrain up to 90% of the neutrinos, thus reducing significantly a model dependence of the neutrino beam prediction.The proposal to collect hadroproduction data on thin and NuMI (Neutrinos at the Main Injector in Fermilab) replica targets exposed to a 120 GeV/c proton beam is reviewed. These data will be used further in neutrino beam calculations for the MINERvA, MINOS(+) and LBNE experiments.

Understanding the HADES dilepton invariant mass spectra with UrQMD simulations

Photons and lepton pairs emerging from decays of virtual photons are the most promising probes of dense hadronic matter. In the energy domain of 1 − 2 GeV per nucleon, HADES has measured electron pairs in C+C, Ar+KCl, p+p, d+p and p+Nb collisions. An experimentally constrained N+N reference spectrum was established. Moreover, for the first time at this energy the inclusive production cross sections for light vector mesons were extracted. This result allows putting tight constraints on vector meson production in heavy-ion collisions at beam energies of a few GeV per nucleon. In this contribution I will compare the HADES data to predictions from UrQMD microscopic transport model calculations and introduce an approach which will allow to separate in a transparent way the generation of the event background from the emission pattern of a physics observable under consideration.

MEKS: A program for computation of inclusive jet cross sections at hadron colliders

EKS is a numerical program that predicts differential cross sections for production of single-inclusive hadronic jets and jet pairs at next-to-leading order (NLO) accuracy in a perturbative QCD calculation. We describe MEKS 1.0, an upgraded EKS program with increased numerical precision, suitable for comparisons to the latest experimental data from the Large Hadron Collider and Tevatron. The program integrates the regularized patron-level matrix elements over the kinematical phase space for production of two and three partons using the VEGAS algorithm. It stores the generated weighted events in finely binned two-dimensional histograms for fast offline analysis. A user interface allows one to customize computation of inclusive jet observables. Results of a benchmark comparison of the MEKS program and the commonly used FastNLO program are also documented. Program SummaryProgram title: MEKS 1.0Catalogue identifier: AEOX_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOX_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland.Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 9234No. of bytes in distributed program, including test data, etc.: 51997Distribution format: tar.gzProgramming language: Fortran (main program), C (CUBA library and analysis program).Computer: All.Operating system: Any UNIX-like system.RAM: ∼300 MBClassification: 11.1.External routines: LHAPDF (https://lhapdf.hepforge.org/)Nature of problem: Computation of differential cross sections for inclusive production of single hadronic jets and jet pairs at next-to-leading order accuracy in perturbative quantum chromodynamics.Solution method: Upon subtraction of infrared singularities, the hard-scattering matrix elements are integrated over available phase space using an optimized VEGAS algorithm. Weighted events are generated and filled into a finely binned two-dimensional histogram, from which the final cross sections with typical experimental binning and cuts are computed by an independent analysis program. Monte Carlo sampling of event weights is tuned automatically to get better efficiency.Running time: Depends on details of the calculation and sought numerical accuracy. See benchmark performance in Section 4. The tests provided take approximately 27 min for the jetbin run and a few seconds for jetana.

SusHi: A program for the calculation of Higgs production in gluon fusion and bottom-quark annihilation in the Standard Model and the MSSM

This article describes the code SusHi (for “Supersymmetric Higgs”) [108] which calculates the cross sections pp/pp¯→ϕ+X in gluon fusion and bottom-quark annihilation in the SM and the MSSM, where ϕ is any of the neutral Higgs bosons within these models. Apart from inclusive cross sections up to NNLO QCD, differential cross sections with respect to the Higgs transverse momentum pT and (pseudo-)rapidity y(η) can be calculated through NLO QCD. In the case of gluon fusion, SusHi contains NLO QCD contributions from the third family of quarks and squarks, NNLO corrections due to top-quarks, approximate NNLO corrections due to top-squarks, and electro-weak effects. It supports various renormalization schemes for the sbottom sector and the bottom Yukawa coupling, as well as resummation effects of higher order tanβ-enhanced sbottom contributions. SusHi provides a link to FeynHiggs for the calculation of the Higgs masses. Program SummaryProgram title: SusHiCatalogue identifier: AEOY_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOY_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 47725No. of bytes in distributed program, including test data, etc.: 338380Distribution format: tar.gzProgramming language: Fortran 77.Computer: Personal computer.Operating system: Unix/Linux, Mac OS.RAM: A few 100 MBClassification: 11.1.External routines: LHAPDF (http://lhapdf.hepforge.org), FeynHiggs (http://www.feynhiggs.de)Nature of problem:Calculation of inclusive and exclusive Higgs production cross sections in gluon fusion and bottom-quark annihilation in the Standard Model and the MSSM through next-to-leading order QCD, includes next-to-next-to-leading order top-(s)quark contributions and electro-weak effectsSolution method:Numerical Monte Carlo integrationAdditional comments:Code includes ggh@nnlo (http://www.robert-harlander.de/software/ggh@nnlo), bbh@nnlo (http://www.robert-harlander.de/software/bbh@nnlo) and evalcsusy.f (http://www.robert-harlander.de/software)Running time:All the examples provided take a minute or less to run.

Strange couplings to the Higgs

We explored the coupling of strange quark to the state of mass close to 126 GeV recently observed by the ATLAS and CMS experiments at the LHC. An enhanced coupling relative to the expectations for a SM Higgs has the effect of increasing both the inclusive production cross section and the partial decay width into jets. For very large modifications, the latter dominates and the net rate into non-jet decay modes such as diphotons is suppressed, with the result that one can use observations of the diphoton decay mode to place an upper limit on the strange quark coupling. We find that the current observations of the diphoton decay mode imply that the coupling of the new resonance to strange quark can be at most ~ 50 times the SM expectation at the 95 % C.L., if one assumes at most a O(1) modification of the coupling to gluons.