Cross Section For Pp Research Articles

Phenomenological analysis of the double-pion production in nucleon-nucleon collisions up to2.2GeV

With an effective Lagrangian approach, we analyze several NN \to NN\pi\pi channels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440)\to N\sigma in the near threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440)\to \Delta\pi, double-Delta, \Delta(1600) \to N*(1440)\pi, \Delta(1600) \to \Delta\pi and \Delta(1620) \to \Delta\pi. There are also sizeable contributions from \Delta \to \Delta\pi, \Delta \to N\pi, N \to \Delta\pi and nucleon pole at energies close to the threshold. We well reproduce the total cross sections up to beam energies of 2.2 GeV except for the pp\to pp\pi^0\pi^0 channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp \to pp\pi^+\pi^-, pp \to nn\pi^+\pi^+ and pp \to pp\pi^0\pi^0 which are measured at CELSIUS and COSY.

Precise measurement of the e+e− → π+π− (γ) cross section with the initial state radiation method at BABAR

We present a precise BABAR measurement on the cross section of the process e+e− → π+π− (γ) from threshold to an energy of 3 GeV with the initial state radiation (ISR) technique, using 232 fb−1 of data collected with the BABAR detector at e+e− center-of-mass energies near 10.58 GeV. The ISR luminosity is determined from a study of the leptonic process e+e− → μ+μ−γ(γ). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the ππ cross section measured from threshold to 1.8 GeV is (514.1 ± 2.2(stat) ±3.1(syst)) × 10−10.

Flavor-Changing Neutral-Current Production of tc̄ in Association with a Neutral Top-Higgs at LHC in the Topcolor-Assisted Technicolor Model

In the framework of the topcolor-assisted technicolor (TC2) model we investigate the flavor-changing neutral-current production pp → tc̄h0t at the Large Hadron Collider (LHC), which proceeds through the parton-level processes gg → tc̄h0t, uū → tc̄h0t and dd → tc̄h0t. We calculate the production rate and present the distributions of the transverse momenta and the invarient mass of the neutral top-higgs. It is found that the cross section of pp → tc̄h0t can reach a few hundreds of fb in a large part of the allowed parameter space. Considering the main decay mode of top-higgs for mht < 2mt, we find that such a production may provide copious events. In the case of unobservation, the LHC can set meaningful constraints on the TC2 model.

Total cross sections of hadron interactions at high energies in a model with low number of constituents

We consider a quantum chromodynamics (QCD)-hadron interaction model in which the gluon density is low in the initial state wave function in rapidity space and real hadrons are produced from color string decay. In this model, the behavior of the total cross sections of pp, p\( \bar p \), π±p, K±p, γp, and γγ interactions is well described. The value of the proton-proton total cross section under the energy of the Large Hadron Collider (LHC) is predicted.

Measurement of the [formula omitted] production cross section and top quark mass extraction using dilepton events in [formula omitted] collisions

We present a measurement of the top quark pair production cross section in pp¯ collisions at s=1.96 TeV using approximately 1 fb−1 collected with the DØ detector. We consider decay channels containing two high pT charged leptons where one lepton is identified as an electron or a muon while the other lepton can be an electron, a muon or a hadronically decaying τ lepton. For a mass of the top quark of 170 GeV, the measured cross section is 7.5−1.0+1.0(stat)−0.6+0.7(syst)−0.5+0.6(lumi) pb. Using ℓτ events only, we measure: σtt¯×B(tt¯→ℓτbb¯)=0.13−0.08+0.09(stat)−0.06+0.06(syst)−0.02+0.02(lumi) pb. Comparing the measured cross section as a function of the mass of the top quark with a partial next-to-next-to leading order Quantum Chromodynamics theoretical prediction, we extract a mass of the top quark of 171.5−8.8+9.9 GeV, in agreement with direct measurements.

Absolute Total np and pp Cross-Section Determinations

Absolute total cross sections for np and pp scattering below 1000 MeV are determined based on partial-wave analyses (PWAs) of nucleon-nucleon scattering data. These cross sections are compared with most recent ENDF/B and JENDL data files, and the Nijmegen PWA. Systematic deviations from the ENDF/B and JENDL evaluations are found to exist in the low-energy region.

FORWARD PHYSICS AT THE LHC: ELASTIC SCATTERING

The following effects in the nearly forward ("soft") region of the LHC are proposed to be investigated: • At small |t| the fine structure of the cone (Pomeron) should be scrutinized: (a) a break of the cone near t ≈ -0.1 GeV 2, due to the two-pion threshold, and required by t-channel unitarity, and (b) possible small-period oscillations between t = 0 and the dip region. • In measuring the elastic pp scattering and total pp cross-section at the LHC, the experimentalists are urged to treat the total cross-section σt, the ratio ρ of real to imaginary part of the forward scattering amplitude, the forward slope B and the luminosity [Formula: see text] as free parameters, and to publish model-independent results on dN/dt. • Of extreme interest are the details of the expected diffraction minimum in the differential cross-section. Its position, expected in the interval 0.4 &lt; -t &lt; 1 GeV 2 at the level of about 10-2 mb · GeV -2–10-1 mb · GeV -2, cannot be predicted unambiguously, and its depth, i.e. the ratio of dσ/dt at the minimum to that at the subsequent maximum (about -t = 5 GeV 2, which is about 5) is of great importance. • The expected slow-down with increasing |t| of the shrinkage of the second cone (beyond the dip-bump), together with the transition from an exponential to a power decrease in -t, will be indicative of the transition from "soft" to "hard" physics. Explicit models are proposed to help in quantifying this transition. • In a number of papers a limiting behavior, or saturation of the black disk limit (BDL), was predicted. This controversial phenomenon shows that the BDL may not be the ultimate limit, instead a transition from shadow to antishadow scattering may by typical of the LHC energy scale.

Elastic and quasi-elastic pp and γ ⋆ p scattering in the dipole model

We have in earlier papers presented an extension of Mueller’s dipole cascade model, which includes sub-leading effects from energy conservation and running coupling as well as color-suppressed saturation effects from pomeron loops via a “dipole swing”. The model was applied to the description of the total and diffractive cross sections in pp and γ * p collisions, and also the elastic cross section in pp scattering. In this paper we extend the model to the description of the corresponding quasi-elastic cross sections in γ * p, namely the exclusive production of vector mesons and deeply virtual Compton scattering. Also for these reactions we find good agreement with measured cross sections. In addition, we obtain a reasonable description of the t-dependence of the elastic pp and quasi-elastic γ ⋆ p cross sections.

Φ PRODUCTION IN pp COLLISIONS

The data for near-threshold cross section for the reaction pp → ppɸ published by the DISTO and ANKE Collaboration are analyzed in order to evaluate the OZI ratio at low energies by taking into account corrections from the kinematics and the final-state interaction. Combining these new data with the few measurements available at higher energies the limit for the OZI rule violation is evaluated and the possible contribution from a five-quark baryonic resonance coupled to the ɸp system is estimated.

Measurement of the Inclusive Jet Cross Section inpp¯Collisions ats=1.96 TeV

We report on a measurement of the inclusive jet cross section in pp[over ] collisions at a center-of-mass energy sqrt[s]=1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70 fb;{-1}. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.

Correlative signatures of heavy Majorana neutrinos and doubly-charged Higgs bosons at the Large Hadron Collider

We explore an intriguing possibility to test the type-II seesaw mechanism of neutrino mass generation at the Large Hadron Collider (LHC). We show that the lepton-number-violating signatures of heavy Majorana neutrinos Ni (for i=1,2,3) and doubly-charged Higgs bosons H±± can be closely correlated with each other in a class of TeV-scale type-II seesaw models. Taking the minimal version of such models for example, we calculate the cross sections of pp→lα±lβ±X processes mediated separately by N1 and H±±, and illustrate their nontrivial correlation at the LHC.

Nucleon charge exchange on the deuteron: A critical review

The existing experimental data on the d(n, p)nn and d(p, n)pp cross-sections in the forward direction are reviewed in terms of the Dean sum rule. It is shown that the measurement of the ratio of the charge exchange on the deuteron to that on the proton might, if taken together with other experimental data, allow a direct construction of the np → np scattering amplitude in the backward direction with few ambiguities.

The TOTEM Experiment at the CERN Large Hadron Collider

The TOTEM Experiment will measure the total pp cross-section with theluminosity-independent method and study elastic and diffractive scattering at the LHC. To achieve optimum forwardcoverage for charged particles emitted by the pp collisions in the interaction point IP5, two tracking telescopes, T1 and T2, will be installed on each sidein the pseudorapidity region 3.1 ⩽ |η| ⩽ 6.5, and Roman Pot stations will be placed at distances of ±147 m and ±220 m from IP5. Being an independent experiment but technically integrated into CMS, TOTEM will first operate in standalone mode to pursue its own physics programme and at a later stage together with CMS for a common physics programme.This article gives a description of the TOTEM apparatus and its performance.

Measurement of thett¯Production Cross Section inpp¯Collisions ats=1.96 TeV

We measure the tt[over] production cross section in pp[over] collisions at sqrt(s)=1.96 TeV in the lepton + jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure sigma(tt[over])=7.62+/-0.85 pb, assuming the current world average m(t)=172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170+/-7 GeV.

Measurement of triple differential photon plus jet cross section by DØ

We report on a new measurement of triple differential cross section for the process pp → γ + jet + X in pp collisions at √s = 1.96 TeV by the DØ Collaboration at Fermilab based on dataset corresponding to an integrated luminosity of 1.1 fb-1.

Kaluza-Klein gluons as a diagnostic of warped models

We study the properties of g{sup 1}, the first excited state of the gluon in representative variants of the Randall-Sundrum (RS) model with the standard model (SM) fields in the bulk. We find that measurements of the coupling to light quarks (from the inclusive cross section for pp-->g{sup 1}-->t[overline t]), the coupling to bottom quarks (from the rate of pp-->g{sup 1}b), as well as the overall width can provide powerful discriminants between the models. In models with large brane kinetic terms, the g{sup 1} resonance can even potentially be discovered decaying into dijets against the large QCD background. We also derive bounds based on existing Tevatron searches for resonant t[overline t] production and find that they require M{sub g{sup 1}} > {approx} 950 GeV. In addition, we explore the pattern of interference between the g{sup 1} signal and the nonresonant SM background, defining an asymmetry parameter for the invariant mass distribution. The interference probes the relative signs of the couplings of the g{sup 1} to light quark pairs and to t[overline t], and thus provides an indication that the top is localized on the other side of the extra dimension from the light quarks, as is typical in the RSmore » framework.« less

Diffractive excitation in DIS andppcollisions

We have in earlier papers presented an extension of Mueller's dipole cascade model, which includes subleading effects from energy conservation and running coupling as well as colour suppressed effects from pomeron loops via a ``dipole swing''. The model was applied to describe the total cross sections in pp and gamma*p collisions. In this paper we present a number of improvements of the model, in particular related to the confinement mechanism. A consistent treatment of dipole evolution and dipole--dipole interactions is achieved by replacing the infinite range Coulomb potential by a screened potential, which further improves the frame-independence of the model. We then apply the model to elastic scattering and diffractive excitation, where we specifically study the effects of different sources for fluctuations. In our formalism we can take into account contributions from all different sources, from the dipole cascade evolution, the dipole--dipole scattering, from the impact-parameter dependence, and from the initial photon and proton wavefunctions. Good agreement is obtained with data from the Tevatron and from HERA, and we also present some predictions for the LHC.

Measurement of the cross sections for π + π − production in pp collisions at energies below 1 GeV

The cross sections for the reaction pp → ppπ + π − are measured at several values of the incident-proton energy. The resulting values are compared with other results, including values obtained previously for a deuteriumtarget, as well as with the predictions of a theoreticalmodel. This comparison reveals that, at energies below 850 MeV, the use of the impulse approximation in extracting the cross sections for double pion production on a free nucleon from data obtained with deuteron targets is illegitimate.

Measurement of thett¯production cross section inpp¯collisions using dilepton events

We present a measurement of the tt¯ pair production cross section in pp¯ collisions at s=1.96 TeV utilizing approximately 425 pb−1 of data collected with the D0 detector. We consider decay channels containing two high pT charged leptons (either e or μ) from leptonic decays of both top-daughter W bosons. These were gathered using four sets of selection criteria, three of which required that a pair of fully identified leptons (i.e., eμ, ee, or μμ) be found. The fourth approach imposed less restrictive criteria on one of the lepton candidates and required that at least one hadronic jet in each event be tagged as containing a b quark. For a top quark mass of 175 GeV, the measured cross section is 7.4±1.4(stat)±1.0(syst) pb and for the current Tevatron average top quark mass of 170.9 GeV, the resulting value of the cross section is 7.8±1.8(stat+syst) pb.2 MoreReceived 4 June 2007DOI:https://doi.org/10.1103/PhysRevD.76.052006©2007 American Physical Society

Flavour structure of low-energy hadron-pair photoproduction

We consider the process γγ→H1H2, where H1 and H2 are either mesons or baryons. The experimental findings for such quantities as the pp and KSKS differential cross sections, in the energy range currently probed, are found often to be in disparity with the scaling behaviour expected from hard constituent scattering. We discuss the long-distance pole–resonance contribution in understanding the origin of these phenomena, as well as the amplitude relations governing the short-distance contribution, which we model as a scaling contribution. When considering the latter, we argue that the difference found for the KSKS and the K+K- integrated cross sections can be attributed to the s-channel isovector component. This corresponds to the ρω→a subprocess in VMD (vector-meson-dominance) language. The ratio of the two cross sections is enhanced by the suppression of the φ component, and it is hence constrained. We give similar constraints to a number of other hadron-pair production channels. After writing down the scaling and pole–resonance contributions respectively, the direct summation of the two contributions is found to reproduce some salient features of the pp and K+K- data.