Muon Cross Section Research Articles

Heavy-flavor hadron decays producing muon cross sections in pp collisions at high transverse momentum

The focus of this work was on investigating and comparing two methods for calculating the cross sections of muons produced by the decay of heavy-flavor hadrons in pp collisions, which cover the interval 2<pT< 20 GeV/c at a center-of-mass energy of s = 7 TeV. One method involves using the fixed-order plus next-to-leading logarithms (FONLL) approach to scale the measured pT-differential cross section of muons from heavy-flavor hadron decay in pp collisions at a center-of-mass energy of s = 5.02 TeV. The other method involves using FONLL calculations to extrapolate the published measured pT-differential cross section at s = 7 TeV to higher pT. In these two methods, we can use the published measured pT-differential cross section at s = 5.02 TeV and s = 7 TeV, which cover the interval 2<pT< 20 GeV/c and 2<pT< 12 GeV/c, respectively. In terms of consistency within uncertainties, the results from both methods were compared not only to pQCD-based FONLL calculations but also to each other. Because they provide the necessary pp reference, these calculations are critical for determining the nuclear modification factor of muons from heavy flavor decays in heavy-ion collisions.

W and Z boson production in p-Pb collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV

The W and Z boson production was measured via the muonic decay channel in proton-lead collisions at sqrt{s_{mathrm{NN}}}=5.02 TeV at the Large Hadron Collider with the ALICE detector. The measurement covers backward (−4.46 < ycms < −2.96) and forward (2.03 < ycms < 3.53) rapidity regions, corresponding to Pb-going and p-going directions, respectively. The Z-boson production cross section, with dimuon invariant mass of 60 < mμμ < 120 GeV/c2 and muon transverse momentum (pTμ) larger than 20 GeV/c, is measured. The production cross section and charge asymmetry of muons from W-boson decays with pTμ > 10 GeV/c are determined. The results are compared to theoretical calculations both with and without including the nuclear modification of the parton distribution functions. The W-boson production is also studied as a function of the collision centrality: the cross section of muons from W-boson decays is found to scale with the average number of binary nucleon-nucleon collisions within uncertainties.

Using wavelet analysis to compare the QCD prediction and experimental data on $$R_{e^+e^-}$$ R e + e - and to determine parameters of the charmonium states above the $$D\bar{D}$$ D D ¯ threshold

The first part of our analysis uses the wavelet method to compare the quantum chromodynamic (QCD) prediction for the ratio of hadronic to muon cross sections in electron-positron collisions, R, with experimental data for R over a center of mass energy range up to about 7 GeV. A direct comparison of the raw experimental data and the QCD prediction is difficult because the data have a wide range of structures and large statistical errors and the QCD description contains sharp quark-antiquark thresholds. However, a meaningful comparison can be made if a type of “smearing” procedure is used to smooth out rapid variations in both the theoretical and experimental values of R. A wavelet analysis (WA) can be used to achieve this smearing effect. The second part of the analysis concentrates on the 3.0–6.0 GeV energy region which includes the relatively wide charmonium resonances $$\psi (1^-)$$ . We use the wavelet methodology to distinguish these resonances from experimental noise, background and from each other, allowing a reliable determination of the parameters of these states. Both analyses are examples of the usefulness of WA in extracting information in a model independent way from high energy physics data.

Measurement of W-boson production in p–Pb collisions at = 5.02 TeV with ALICE at the LHC

In hadronic collisions, electroweak bosons are produced in initial hard scattering processes and they are not affected by the strong interaction. In proton-proton collisions, they have been suggested as standard candles for luminosity monitoring and their measurement can improve the evaluation of detector performances. In nucleus-nucleus and proton-nucleus collisions, W-bosons allow one to check at first order the validity of binary collision scaling, while small deviations allow to study the nuclear modifications of parton distribution functions. The W-boson production in p-Pb collisions at = 5.02 TeV is measured via the contribution of W-boson decays to the inclusive pT-differential muon yield reconstructed with the ALICE muon spectrometer at forward (2.03 < yμcms < 3.53) and backward (-4.46 < yμcms < -2.96) rapidity. This paper reports the production cross section of muons from W-boson decays for pμT > 10 GeV/c and the yields normalised to the average number of binary nucleon-nucleon collisions as a function of the event activity.

Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at $\sqrt{s}$ = 7 TeV with the ATLAS detector

We present the measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of $\sqrt{s} = $ 7 TeV, using ∼1.4 pb − 1 of data collected by the ATLAS detector at the Large Hadron Collider. The muon cross-section is measured as a function of muon transverse momentum p T in the range 4 < p T < 100 GeV and within pseudorapidity |η| < 2.5. In addition, the electron and muon cross-sections are measured in the range 7 < p T < 26 GeV and within |η| < 2.0, excluding 1.37 < |η| < 1.52. After subtraction of the W/Z/γ ∗ contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from fixed order NLO calculations with NLL high-p T resummation, and to be sensitive to the effects of NLL resummation.

Production of Muons from Heavy Flavor Decays at Forward Rapidity inppand Pb-Pb Collisions atsNN=2.76 TeV

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5<y<4, in pp and Pb-Pb collisions at sqrt[s(NN)]=2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6<p(t)<10 GeV/c. The suppression shows no significant p(t) dependence.

Measurements of the electron and muon inclusive cross-sections in proton–proton collisions at [formula omitted] with the ATLAS detector

This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of s=7 TeV, using data collected by the ATLAS detector at the LHC. The muon cross-section is measured as a function of pT in the range 4<pT<100 GeV and within pseudorapidity |η|<2.5. In addition the electron and muon cross-sections are measured in the range 7<pT<26 GeV and within |η|<2.0, excluding 1.37<|η|<1.52. Integrated luminosities of 1.3 pb−1 and 1.4 pb−1 are used for the electron and muon measurements, respectively. After subtraction of the W/Z/γ⁎ contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLO calculations with NLL high-pT resummation, and to be sensitive to the effects of NLL resummation.

Heavy flavour production in the semi-muonic channel at forward rapidity in pp collisions at = 7 TeV and Pb–Pb collisions at = 2.76 TeV with ALICE

Heavy quark production is measured in the single-muon decay channel with the ALICE muon spectrometer. We present the differential production cross section of muons from heavy flavour decay at forward rapidity (2.5 < y < 4) in pp collisions at TeV and comparisons to perturbative QCD predictions. The analysis of the inclusive muon production in Pb–Pb collisions at TeV is described as well, and special attention is given to preliminary results on the nuclear modification factor.

Muon cross-sections with both the LPM effect and the Ter-Mikayelyan effect at extremely high energies

Differential and integral muon cross-sections are calculated in water, standard rock, iron and lead, with and without the LPM effect. The corresponding cross-sections are also calculated with the dielectric suppression effect (Ter-Mikayelyan effect), in addition to the LPM effect. In our calculations the LPM effect for muons is significant from 1014 eV to 1022 eV, depending on the material, for bremsstrahlung, while it is completely negligible in the direct pair production process up to 1022 eV even for lead. The dielectric suppression effect is only important between 1012 eV and 1020 eV in the case with the LPM effect, while it is significant above 1012 eV in the case without the LPM effect.

Small-Angle Muon and Bottom-Quark Production inpp¯Collisions at√s=1.8TeV

This Letter describes a measurement of the muon cross section originating from b-quark decay in the forward rapidity range 2.4<| y(&mgr;)|<3.2 in p&pmacr; collisions at sqrt[s] = 1.8 TeV. The data used in this analysis were collected by the D0 experiment at the Fermilab Tevatron. We find that next-to-leading-order QCD calculations underestimate b-quark production by a factor of 4 in the forward rapidity region.

Tevatron direct photon results

Tevatron direct photon results since DIS98 are reviewed. Two new CDF measurements are discussed, the Run Ib inclusive photon cross section and the photon+muon cross section. Comparisons with the latest NLO QCD calculations are presented.

Pion and neutron production by cosmic-ray muons underground.

The production of positive pions and neutrons by cosmic muons at underground sites of various depths is investigated. We first test the equivalent photon method in the particular case of \ensuremath{\Delta} excitation by the muon. We find that this method, when it neglects the momentum dependence of the transverse response, reproduces remarkably well the theoretical muon cross section. This success has lead us to apply the method to higher energies, where it has not been tested. We evaluate in this way the production of positive pions in liquid scintillator from known photo-absorption cross sections. At a shallow depth of 20 meters our estimate reproduces the measurement. As for the neutron emission, we include the obvious sources, such as the giant-resonance excitation, the quasideuteron process, the quasifree pion production as well as neutrons emitted following pion capture. Our evaluation underestimates the number of neutrons produced and finds a too weak dependence on the depth. This suggests that secondary neutron production is important at all depths.

Minijets and associated production of photons and muons in high energy heavy ion collisions

Due to the large hadronic multiplicities involved in heavy ion collisions at LHC energies, production of photons and muons inside jets cannot be distinguished from production in isolation. Associated production rates for photons and muons in minijets are estimated. It is found that the muon cross section per uranium-uranium collision could be substantial.

A measurement of the total cross section and a study of inclusive muon production for the process e +e −→ hadrons in the energy range between 39.79 GeV and 46.78 GeV

The total cross section and the inclusive muon cross section for the process e +e −→ hadrons have been measured in the center of mass energy range between 39.79 and 46.78 GeV. The ratio R shows no significant structure. It has an average value of 4.13±0.08±0.14. An upper limit is set on the production of narrow resonances. Limits are obtained for pair-produced heavy quarks. The data are compared with the standard electroweak interaction model including QCD corrections taking into account the five known types of quarks. Upper limits are given for a possible structure of quarks and for effects of color octet leptons.

A study of double tagged two-photon reactions at spear

We have identified 262 doubly tagged two-photon events. A subset of the data shows an enhancement of 21 events in the inclusive two-photon mass squared distribution between 0.8 and 2.2 GeV 2. If these events result from spin 2 resonance production then Γ γγ = 9.5 ± 3.9 ± 2.4 keV (statistical and systematic). From another subset of 58 events in which the final state could be classified we determine the two-photon hadron to muon cross section ratio R γγ = 1.1 ± 0.3 ± 0.3.

Cross sections for scalar W-meson and vector W-meson production by muons and neutrinos

Following a recent proposal, cross sections for scalar W-mesons and vector W-mesons are calculated for different combinations of the masses of these two W-mesons. It is found, for M S much smaller than M V and the lab energy not too large, that scalar meson production cannot be neglected in comparison to vector meson production. The scalar neutrino cross sections are only a factor two to five larger than the equivalent muon cross sections.

Coherent, incoherent and inelastic cross sections for W-meson production by muons and neutrinos

Cross sections for W-meson production by muons and neutrinos are calculated for vector-boson masses of 3 and 6 GeV and incident lepton energies of 50, 75 and 100 GeV. It is found that muon cross sections are up to a factor 1000 smaller than the corresponding neutrino cross sections, that W-mesons produced by muons are not polarized, while W-mesons produced by neutrinos are left-handed polarized, that in both processes the total inelastic cross sections are of the same order as the incoherent cross sections, and the σ(N) ∗ (i.e. the parts of the inelastic cross sections referring to N ∗) form a very small part of the total inelastic cross sections. The inelastic cross sections are calculated with the form factors W 1 and W 2, where the SLAC data are used. We modify W 1 so that it is consistent with positive definiteness and use scaling.

Inelastic Nuclear Interactions of High-Energy Electrons and Muons in Emulsion

An experiment has been carried out to examine the inelastic nuclear interaction properties of high-energy electrons and muons in emulsion. A study was made of interactions produced by 10.5-GeV muons and 10.0- and 16.0-GeV electrons. Total and differential cross sections have been measured and compared with calculations carried out with the formulation of Hand and Wilson for inelastic lepton scattering. On the basis of the calculations, the ratio of electron to muon total cross sections was found to be 3.5:1, whereas experimentally the ratio was measured to be 2.18\ifmmode\pm\else\textpm\fi{}0.40 for the 10-GeV leptons. To explain the total cross section for electrons, an average scalar-photon contribution equal to 12% of the transverse-photon cross section is needed, which is consistent with other experiments. The muon cross section was found to be significantly larger than expected, and it cannot be explained by a similar scalar-photon contribution. The energy dependence of the total cross sections is in agreement with theory, as are the angular distributions of the scattered leptons.