Hadronic Cross Sections Research Articles

Total Hadronic Cross-Section Data and the Froissart–Martin Bound

The energy dependence of the total hadronic cross section at high energies is investigated with focus on the recent experimental result by the TOTEM Collaboration at 7 TeV and the Froissart-Martin bound. On the basis of a class of analytical parametrization with the exponent $\gamma$ in the leading logarithm contribution as a free parameter, different variants of fits to $pp$ and $\bar{p}p$ total cross section data above 5 GeV are developed. Two ensembles are considered, the first comprising data up to 1.8 TeV, the second also including the data collected at 7 TeV. We shown that in all fit variants applied to the first ensemble the exponent is statistically consistent with $\gamma$ = 2. Applied to the second ensemble, however, the same variants yield $\gamma$'s above 2, a result already obtained in two other analysis, by U. Amaldi \textit{et al}. and by the UA4/2 Collaboration. As recently discussed by Ya. I. Azimov, this faster-than-squared-logarithm rise does not necessarily violate unitarity. Our results suggest that the energy dependence of the hadronic total cross section at high energies still constitute an open problem.

Electroweak radiative corrections to Higgs production via vector boson fusion using soft-collinear effective theory: Numerical results

Electroweak radiative corrections are computed for Higgs production through vector boson fusion, qq->qqH, which is one of the most promising channels for detecting and studying the Higgs boson at the LHC. Using soft-collinear effective theory, we obtain numerical results for the resummed logarithmic contributions to the hadronic cross section at next-to-leading logarithmic order. We compare our results to HAWK and find good agreement below 2 TeV where the logarithms do not dominate. The SCET method is at its best in the high LHC energy domain where the corrections are found to be slightly larger than predicted by HAWK and by other one-loop fixed order approximations. This is one of the first tests of this formalism at the level of a hadronic cross section, and demonstrates the viability of obtaining electroweak corrections for generic processes without the need for difficult electroweak loop calculations.

Asymptotic energy dependence of hadronic total cross sections from lattice QCD

The nonperturbative approach to soft high-energy hadron-hadron scattering, based on the analytic continuation of Wilson-loop correlation functions from Euclidean to Minkowskian theory, allows to investigate the asymptotic energy dependence of hadron-hadron total cross sections in lattice QCD. In this paper we will show, using best fits of the lattice data with proper functional forms satisfying unitarity and other physical constraints, how indications emerge in favor of a universal asymptotic high-energy behavior of the kind B log^2 s for hadronic total cross sections.

Determination of Hadronic Interaction Characteristics with the Pierre Auger Observatory

The Pierre Auger Observatory measures extensive air showers (EAS) up to the highest energies. One of the biggest challenges in current data analyses is to interpret these data in terms of the primary mass composition. Due to the insufficient constraint of interactions in EAS this is afflicted with large uncertainties. On the other hand, this high sensitivity of EAS to interaction features can be exploited to determine or constrain properties of interactions up to of 450 TeV. We demonstrate how specific EAS observations are suited for this task and thus may contribute to limit the uncertainties in the interpretation of air showers. These are the estimation of the muon number at ground level and the study of the hadronic cross section for particle production via EAS fluctuations.

The fully differential hadronic production of a Higgs boson through bottom-quark fusion at NNLO

The fully differential computation of the hadronic production cross section of a Higgs boson via bottom quarks is presented at NNLO in QCD. Several differential distributions with their corresponding scale uncertainties are presented for the 8 TeV LHC. This is the first application of the method of non-linear mappings for NNLO differential calculations at hadron colliders.

PHOTON-PROTON TOTAL CROSS SECTION AND FACTORIZATION PROCESS

A fit for photon-proton total cross section ( ) data in terms of Regge model has been obtained. As usual the fit can be obtained by calculating the coupling constants of the exchanged Reggeons and pomerons in the process. The model has three Regge components, the low energy region is dominated by meson and the high energy region is dominated by the soft and hard pomerons. As Regge pole factorizes the hadronic total cross sections are related by factorization. A fit for the photon -photon total cross section ( ) can also be obtained by the factorization.

Publisher’s Note: Total hadronic cross sections andπ∓π+scattering [Phys. Rev. D85, 074020 (2012)

Publisher’s Note: Total hadronic cross sections and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>π</mml:mi><mml:mo>∓</mml:mo></mml:msup><mml:msup><mml:mi>π</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>scattering [Phys. Rev. D<b>85</b>, 074020 (2012)

Associated production ofZand neutral Higgs bosons at the CERN Large Hadron Collider

We study the hadroproduction of a CP-even or CP-odd neutral Higgs boson in association with a Z boson in the minimal supersymmetric extension of the standard model (MSSM) We include the contributions from quark-antiquark annihilation at the tree level and those from gluon-gluon fusion, which proceeds via quark and squark loops, and list compact analytic results. We quantitatively analyze the hadronic cross sections at the CERN Large Hadron Collider assuming a favorable supergravity-inspired MSSM scenario.

Z′near theZ-pole

We present a fit to precision electroweak data in the standard model (SM) extended by an additional vector boson, ${Z}^{\ensuremath{'}}$, with suppressed couplings to the electron compared to the $Z$ boson, with couplings to the $b$-quark, and with mass close to the mass of the $Z$ boson. This scenario provides an excellent fit to forward-backward asymmetry of the $b$-quark measured on the $Z$-pole and $\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{GeV}$ off the $Z$-pole, and to lepton asymmetry, ${A}_{e}$, obtained from the measurement of left-right asymmetry for hadronic final states, and thus it removes the tension in the determination of the weak mixing angle from these two measurements. It also leads to a significant improvement in the total hadronic cross-section on the $Z$-pole and ${R}_{b}$ measured at energies above the $Z$-pole. We explore in detail properties of the ${Z}^{\ensuremath{'}}$ needed to explain the data and present a model for ${Z}^{\ensuremath{'}}$ with required couplings. The model preserves standard model Yukawa couplings; it is anomaly-free and can be embedded into grand unified theories. It allows a choice of parameters that does not generate any flavor violating couplings of the ${Z}^{\ensuremath{'}}$ to standard model fermions. Out of standard model couplings, it only negligibly modifies the left-handed bottom quark coupling to the $Z$ boson and the third column of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix. Modifications of standard model couplings in the charged lepton sector are also negligible. It predicts an additional down-type quark, $D$, with mass in the few hundred GeV range, and an extra lepton doublet, $L$, possibly much heavier than the $D$-quark. We discuss signatures of the ${Z}^{\ensuremath{'}}$ at the Large Hadron Collider and calculate the ${Z}^{\ensuremath{'}}b$ production cross-section, which is the dominant production mechanism for the ${Z}^{\ensuremath{'}}$.

Total hadronic cross sections andπ∓π+scattering

Recent measurements of the inelastic and total proton-proton cross section at the LHC, and at cosmic ray energies by the Auger experiment, have quantitatively confirmed fits to lower energy data constrained by the assumption that the proton is asymptotically a black disk of gluons. We show that data on \bar p(p)p,\pi^\mp p, and K^\mp p forward scattering support the related expectation that the asymptotic behavior of all cross sections is flavor independent. By using the most recent measurements from ATLAS, CMS, TOTEM and Auger, we predict \sigma^{pp}_{\rm tot} (\sqrt s=8 {\rm TeV})=100.6 \pm 2.9 mb and \sigma^{pp}_{\rm tot} (\sqrt s=14 {\rm TeV})=110.8 \pm 3.5 mb, as well as refine the total cross section \sigma^{pp}_{\rm tot} (\sqrt s=57 {\rm TeV})=139.6 \pm 5.4 mb. Our analysis also predicts the total \pi^\mp \pi^+ cross sections as a function of \sqrt s.

KLOE results on hadronic cross section

The KLOE experiment at the ϕ – factory DAΦNE is the first to have exploited Initial State Radiation (ISR) to precisely determine the e+e− → π+π−(γ) cross section below 1 GeV, representing the 70% of the leading order contribution to the muon anomaly. The leading order contribution ahloμ is presently the main source of uncertainty in the theoretical evaluation of the muon anomaly, and it can be evaluated by dispersion integral using the experimental measurement of hadronic cross section. A persistent discrepancy of about 3 σ between standard model (SM) prediction and experimental measurements of the muon anomalous magnetic moment has been up to now observed. The KLOE collaboration published two measurements of the π+π− cross section with the photon in the initial state emitted at small polar angle in Phys. Lett. B vol. 606 pg. 12 and vol. 670 pg. 285, and an independent measurement with the photon emitted at large polar angle in Phys. Lett. B vol. 700 pg. 102. These measurements were normalized to the DAΦNE luminosity. Recently, a new analysis deriving the pion form factor directly from measuring the bin-by-bin π+πγ and μ+μγ final states ratio has been performed. In this paper, the preliminary results of this new measurement and the comparison to the previous published ones, the impact on the evaluation of the hadronic contribution to the muon anomaly, the preliminary μ+μγ cross section measurement and the comparison with the PHOKHARA-MC prediction are presented.

Latest on g-2 from experiment

I will review the latest experimental achievements on the hadronic cross section measurements at low-energy which are of fundamental importance for a precise evaluation of the hadronic contribution to the g-2 of the muon. Then I will discuss the new proposed muon g-2 experiments, with particular emphasis on E989 at Fermilab which plans to improve the experimental uncertainty of a factor 4 respect to the previous E821 experiment at BNL.

Harmonic decomposition of two particle angular correlations in Pb–Pb collisions at [formula omitted

Angular correlations between unidentified charged trigger (t) and associated (a) particles are measured by the ALICE experiment in Pb–Pb collisions at sNN=2.76 TeV for transverse momenta 0.25<pTt,a<15 GeV/c, where pTt>pTa. The shapes of the pair correlation distributions are studied in a variety of collision centrality classes between 0 and 50% of the total hadronic cross section for particles in the pseudorapidity interval |η|<1.0. Distributions in relative azimuth Δϕ≡ϕt−ϕa are analyzed for |Δη|≡|ηt−ηa|>0.8, and are referred to as “long-range correlations”. Fourier components VnΔ≡〈cos(nΔϕ)〉 are extracted from the long-range azimuthal correlation functions. If particle pairs are correlated to one another through their individual correlation to a common symmetry plane, then the pair anisotropy VnΔ(pTt,pTa) is fully described in terms of single-particle anisotropies vn(pT) as VnΔ(pTt,pTa)=vn(pTt)vn(pTa). This expectation is tested for 1⩽n⩽5 by applying a global fit of all VnΔ(pTt,pTa) to obtain the best values vn{GF}(pT). It is found that for 2⩽n⩽5, the fit agrees well with data up to pTa∼3–4 GeV/c, with a trend of increasing deviation as pTt and pTa are increased or as collisions become more peripheral. This suggests that no pair correlation harmonic can be described over the full 0.25<pT<15 GeV/c range using a single vn(pT) curve; such a description is however approximately possible for 2⩽n⩽5 when pTa<4 GeV/c. For the n=1 harmonic, however, a single v1(pT) curve is not obtained even within the reduced range pTa<4 GeV/c.

Total hadronic cross section and the elastic slope: An almost model-independent connection

An almost model-independent parametrization for the ratio of the total cross section to the elastic slope, as function of the center of mass energy, is introduced. The analytical result is based on the approximate relation of this quantity with the ratio R of the elastic to total cross section and empirical fits to the R data from proton–proton scattering above 10 GeV, under the conditions of asymptotic unitarity and the black-disk limit. This parametrization may be useful in studies of extensive air showers and the determination of the proton–proton total cross section from proton–air production cross section in cosmic-ray experiments.

The effect of Higgs boson radiation from TeV black holes on the hadronic cross section at the LHC

In curved space–time near TeV black holes many gluons and quarks produced by the Unruh effect interact with each other and create Higgs bosons. We study the Unruh effect and show that, for gluons and quarks, the internal stationary state of a Schwarzschild black hole can be represented by a maximally entangled two-mode squeezed state of outgoing and infalling Hawking radiation. We consider different channels for Higgs boson production near event horizons of mini black holes at the Large Hadron Collider (LHC) and obtain the cross section in each channel. We observe that the cross section of a Higgs boson produced via gluon fusion near a single black hole is much larger for smaller black hole masses. This is because the temperature of the black hole becomes larger as the mass becomes smaller and the thermal radiation of the gluons is enhanced. At lower mass, MBH &lt; 4 TeV, the black hole will not be able to emit Higgs, but will still be able to produce a quark; for MBH &lt; 3 TeV the black hole can only emit massless gluons. We show that as the black hole mass at the LHC increases (4 TeV &lt; MBH &lt; 8 TeV) most of the Higgs boson production is due to the Unruh effect near the event horizon of the black hole. Comparing these Higgs boson cross sections with Higgs boson cross sections in perturbative quantum chromodynamics, we find that micro black holes can be a source of Higgs production at the LHC. Finally, we calculate the effects of Higgs boson radiation due to mini black holes on the hadronic cross section at the LHC. We observe that as the order of perturbation theory increases this effect becomes systematically more significant because at higher orders there exist more channels for Higgs production and, in our calculations, Higgs decay into massive quark–antiquark pairs. At smaller masses, MBH &lt; 2 TeV, the hadronic cross section at leading order is large while the cross sections at next-to-leading order and at next-to-next-to-leading order are rising at MBH ∼ 2 and 3 TeV, respectively, and exhibit a turn-over at moderate values of black hole mass.

Hadronic Cross Sections for Neutrino Production in MIPP

Hadronic Cross Sections for Neutrino Production in MIPP

Vector correlators in lattice QCD: Methods and applications

We discuss the calculation of the leading hadronic vacuum polarization in lattice QCD. Exploiting the excellent quality of the compiled experimental data for the e^+e^- --> hadrons cross-section, we predict the outcome of large-volume lattice calculations at the physical pion mass, and design computational strategies for the lattice to have an impact on important phenomenological quantities such as the leading hadronic contribution to (g-2)mu and the running of the electromagnetic coupling constant. First, the R(s) ratio can be calculated directly on the lattice in the threshold region, and we provide the formulae to do so with twisted boundary conditions. Second, the current correlator projected onto zero spatial momentum, in a Euclidean time interval where it can be calculated accurately, provides a potentially critical test of the experimental R(s) ratio in the region that is most relevant for (g-2)mu. This observation can also be turned around: the vector correlator at intermediate distances can be used to determine the lattice spacing in fm, and we make a concrete proposal in this direction. Finally, we quantify the finite-size effects on the current correlator coming from low-energy two-pion states and provide a general parametrization of the vacuum polarization on the torus.

A model for probing large distance behaviour in high energy collisions

We apply to total cross-sections our model for soft gluon resummation in the infrared region. The model aims to probe large distance interactions in QCD. Our ansatz for an effective coupling for gluons and quarks in the infrared region follows an inverse power law which is singular but integrable. In the context of an eikonal formalism with QCD mini-jets, we study total hadronic cross-sections for protons, pions, photons. We estimate the total inelastic cross-section at LHC comparing with recent measurements and update previous results for survival probability.

Hadron production from μ–Deuteron scattering at [formula omitted] at COMPASS

Hadrons proceeding from quasi-real photo-production are one of the many probes accesible at the Common Muon Proton Apparatus for Structure and Spectroscopy (COMPASS) at CERN. These hadrons provide information on the scattering between photon and partons through γ-gluon(g) direct channels as well as q-g resolved processes. Comparisons of unpolarized differential cross section measurements to next-to-leading order (NLO) pQCD calculations are essential to develop our understanding of proton-proton and lepton-nucleon scattering at varying center of mass energies. These measurements are important to asses the applicability of NLO pQCD in interpreting polarized processes. In this talk we will present the unidentified charged separated hadron cross-sections measured by the COMPASS experiment at center of mass energy of √ s = 17 GeV ,l owQ 2 (Q 2 1.0 GeV/c.)

Hadronic absorption cross sections ofBc

The cross sections of $B_{c}$\ absorption by $\pi $ mesons are calculated using hadronic Lagrangian based on SU(5) flavor symmetry. Calculated cross sections are found to be in range 2 to 7 mb and 0.2 to 2 mb for the processes $B_{c}^{+}\pi \rightarrow DB$ and $B_{c}^{+}\pi \rightarrow D^{\ast}B^{\ast}$ respectively, when the monopole form factor is included. These results could be useful in calculating production rate of $B_{c}$ meson in relativistic heavy ion collisions.