Cross Section For Pp Research Articles

Baryon electromagnetic form factors at BESIII

Electromagnetic form factors are fundamental quantities which parameterize the electric and magnetic structure of hadrons. This contribution reports on the measurements of baryon electromagnetic form factors at the BESIII experiment in Beijing. The Beijing e + e − collider BEPCII is a double-ring symmetric collider running at √s between 2.0 and 4.6 GeV. Baryon electromagnetic form factors can be measured at BESIII in direct e + e − -annihilation and in initial state radiation processes. Based on the data collected by the BESIII detector at 12 center of mass energies between 2.23 and 3.67 GeV, the e + e − → pp cross section and the time-like proton form factor is measured. Preliminary results from the analysis of the initial state radiation process e + e − → ppγ using a data set of 7.408 fb−1 collected at center-of-mass energies between 3.773 and 4.6 GeV, are also presented. The cross section for is measured based on 40.5 pb−1 data collected at 4 energy points from the threshold up to 3.08 GeV. Preliminary results on the total cross section and the Λ effective form factor are shown. Ongoing analysis based on the high luminosity energy scan from 2015 and from radiative return at different √s are also described.

Effects of diffraction in pp and pA collisions

Diffractive excitation is a large fraction of the pp cross section, also at high energies. Diffraction has been described by multi-Regge diagrams, or in the Good-Walker formalism as a result of fluctuations. The two formalisms are, however, just different sides of the same phenomenon. The dipole cascade formalism in impact parameter space is well suited to describe diffractive excitation including effects of saturation. Diffractive excitation is also an important effect in pA scattering, where the Glauber formalism has been used to estimate the number of NN subcollisions and of “wounded” nucleons. Diffractive excitation has here been either neglected or included in a simplified way, not including excitation of target nucleons. In this talk we discuss how these effects can be included with the help of the dipole cascade model DIPSY.

Measurement of the total cross section from elastic scattering in pp collisions at [formula omitted] with the ATLAS detector

In this contribution a measurement of the total pp cross section with the ATLAS detector at the LHC at s=7 TeV is presented. In a special run with high-β⋆ beam optics, the differential elastic cross section is measured as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the |t| range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to |t|→0, the total cross section, σtot(pp→X), is measured via the optical theorem to be:σtot(pp→X)=95.35±0.38(stat.)±1.25(exp.)±0.37(extr.) mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to |t|→0. In addition, the slope of the elastic cross section at small |t| is determined to be B = 19.73 ± 0.14 (stat.) ± 0.26 (syst.) GeV-2.

E6inspired composite Higgs model and 750 GeV diphoton excess

In the E6 inspired composite Higgs model (E6CHM) the strongly interacting sector possesses an SU(6)\times U(1)_B\times U(1)_L global symmetry. Near scale f\gtrsim 10 TeV the SU(6) symmetry is broken down to its SU(5) subgroup, that involves the standard model (SM) gauge group. This breakdown of SU(6) leads to a set of pseudo--Nambu--Goldstone bosons (pNGBs) including a SM--like Higgs and a SM singlet pseudoscalar A. Because of the interactions between A and exotic fermions, which ensure the approximate unification of the SM gauge couplings and anomaly cancellation in this model, the couplings of the pseudoscalar A to gauge bosons get induced. As a result, the SM singlet pNGB state A with mass around 750 GeV may give rise to sufficiently large cross section of pp\to \gamma\gamma that can be identified with the recently observed diphoton excess.

Large Rapidity Gap Method to Select Soft Diffraction Dissociation at the LHC

In proton-proton (pp) collisions, any process involves exchanging the vacuum quantum numbers is known as diffractive process. A diffractive process with no largeQ2is called soft diffractive process. The diffractive processes are important for understanding nonperturbative QCD effects and they also constitute a significant fraction of the total pp cross section. The diffractive events are typically characterized by a region of the detector without particles, known as a rapidity gap. In order to observe diffractive events in this way, we consider the pseudorapidity acceptance in the forward region of the ATLAS and CMS detectors at the Large Hadron Collider (LHC) and discuss the methods to select soft diffractive dissociation for pp collisions ats=7 TeV. It is shown that, in the limited detector rapidity acceptance, it is possible to select diffractive dissociation events by requiring a rapidity gap in the event; however, without using forward detectors, it seems not possible to fully separate single and double diffractive dissociation events. The Zero Degree Calorimeters can be used to distinguish the type of the diffractive processes up to a certain extent.

Simultaneous analysis of neutrinoless double beta decay and LHC pp-cross sections: limits on the left-right mixing angle

The extension of the Standard Model of electroweak interactions, to accommodate massive neutrinos and/or right-handed currents, is one of the fundamental questions to answer in the cross-field of particle and nuclear physics. The consequences of such extensions would reflect upon nuclear decays, like the very exotic nuclear double-beta-decay, as well as upon high-energy proton-proton reactions of the type performed at the LHC accelerator. In this talk we shall address this question by looking at the results reported by the ATLAS and CMS collaborations, where the excitation and decay of a heavy-mass boson may be mediated by a heavy-mass neutrino in proton-proton reactions leading to two jets and two leptons, and by extracting limits on the left-right mixing, from the latest measurements of nuclear-double-beta decays reported by the GERDA and EXO collaborations.

Measurement of diffractive dissociation cross sections inppcollisions ats=7 TeV

Measurements of diffractive dissociation cross sections in pp collisions at sqrt(s) = 7 TeV are presented in kinematic regions defined by the masses M[X] and M[Y] of the two final-state hadronic systems separated by the largest rapidity gap in the event. Differential cross sections are measured as a function of xi[X]= M[X]^2/s in the region -5.5 < log[10]xi[X] < -2.5, for log[10]M[Y] < 0.5, dominated by single dissociation (SD), and 0.5 < log[10]M[Y] < 1.1, dominated by double dissociation (DD), where M[X] and M[Y] are given in GeV. The inclusive pp cross section is also measured as a function of the width of the central pseudorapidity gap Delta eta for Delta eta > 3, log[10]M[X] > 1.1, and log[10]M[Y] > 1.1, a region dominated by DD. The cross sections integrated over these regions are found to be, respectively, 2.99 +/- 0.02 (stat) +0.32 -0.29 (syst) mb, 1.18 +/- 0.02 (stat) +/- 0.13 (syst) mb, and 0.58 +/- 0.01 (stat) +0.13 -0.11 (syst) mb, and are used to extract total SD and DD cross sections. In addition, the inclusive differential cross section, d sigma /d Delta eta[F], for events with a pseudorapidity gap adjacent to the edge of the detector, is measured over Delta eta[F] = 8.4 units of pseudorapidity. The results are compared to those of other experiments and to theoretical predictions, and found compatible with slowly-rising diffractive cross sections as a function of center-of-mass energy.

Theoretical remarks on diffraction at the LHC

We comment on the nonperturbative nature of the total cross-section in pp scattering and on the importance of the survival probability for the understanding of diffractive final states in pp scattering.

Medium effects on the transport coefficients of a hot pion gas

The study of transport properties of strongly interacting matter has captured much attention in recent times. The interpretation of experimentally measured elliptic flow of hadrons in RHIC, by nearly ideal hydrodynamics with a small value of η/s, close to the quantum bound 1/4π, provides much interest towards the transport coefficients, which characterize the response of an out of equilibrium system to certain disturbances. Our aim is to determine the shear and bulk viscous coefficients and as well as the thermal conductivity for an interacting pion gas by solving relativistic transport equation in kinetic theory approach. For the dynamical input we need to construct a medium dependent ππ cross-section which gives noticeable effects on the temperature of viscous coefficients and thermal conductivity.

Measurement of the inelastic pp cross-section at a centre-of-mass energy of s $$ \sqrt{s} $$ = 7 TeV

The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum $p_{\rm T}>0.2$ GeV/$c$ in the pseudorapidity range $2.0<\eta<4.5$, is measured by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=7$ TeV. The cross-section in this kinematic range is determined to be $\sigma_{\rm inel}^{\rm acc} = 55.0 \pm 2.4$ mb within the spectrometer acceptance with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using PYTHIA 6, yields $\sigma_{\rm inel} = 66.9 \pm 2.9 \pm 4.4$ mb, where the first uncertainty is experimental and the second is due to the extrapolation.

Diffraction and Forward Physics in ATLAS: results and perspectives

1 I.N.F.N. Sezione di Bologna (ITALY) Abstract. The present and future potential of ATLAS for diffraction and forward physics is presented. As recent results the rapidity gap cross section and elastic and total pp cross sections are reported. The upgrade project AFP is presented and it is shown how it will complement the ALFA acceptance for diffractive physics in mea- surements taken with β ∗ =90 m LHC beam optics. Moreover, the AFP detector will guarantee good acceptance on diffractive events also during normal running conditions allowing to improve the ATLAS detector perfor- mances. If in addition, a high luminosity program will be feasible, AFP might be fundamental for potential discoveries with extra dimensions being one example.

T dependence of the slope of the high energy elastic pp cross section

We consider the main factors which cause the variation of the value of the local slope of the elastic cross section with t. Namely, we discuss the role of the pion loop insertion in the pomeron trajectory, the t-dependence of the pomeron–nucleon coupling and the role of the eikonalization of the proton–proton amplitude in both the one- and two-channel eikonal models.

Colisiones elásticas y sección eficaz total hadrón - hadrón a altas energías

We present a study of the differential cross section for pp and pp collisions based on the use of a parametrization of the scattering amplitude as a function of two exponential terms with a phase difference. This parametrization describes correctly the experimental data, including the diffraction minimum which is different for both processes.Also, a detailed study of the total cross section, σT, for pp, pp, π±p and K±p collisions is presented. This study uses a parametrization based on the logaritmic increase of σT with the energy of the collision. Integral dispersion relations are used in order to maximize the data sample tudied. All the existing experimental data up to date (including datafrom the TOTEM experiment) are taken into account. The study concludes that σT increases with energy as ln 2(s) and predicts a value for σT in pp collisions at the energy of 14 TeV of σpp = 109,1 ± 1,6 mb.T The document aditionally presents a review of the methods used to study elastic collis. © 2014. Acad. Colomb. Cienc. Ex. Fis. Nat. All rights reserved.

CBM Collaboration

Using 2917pb−1 of data accumulated at 3.773GeV, 44.5pb−1 of data accumulated at 3.65GeV and data accumulated during a ψ(3770) line-shape scan with the BESIII detector, the reaction e+e−→pp¯ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of e+e−→ψ(3770)→pp¯, σ(e+e−→ψ(3770)→pp¯), is found to have two solutions, determined to be (0.059−0.020+0.070±0.012)pb with the phase angle ϕ=(255.8−26.6+39.0±4.8)° (<0.166pb at the 90% confidence level), or σ(e+e−→ψ(3770)→pp¯)=(2.57−0.13+0.12±0.12)pb with ϕ=(266.9−6.3+6.1±0.9)° both of which agree with a destructive interference. Using the obtained cross section of ψ(3770)→pp¯, the cross section of pp¯→ψ(3770), which is useful information for the future PANDA experiment, is estimated to be either (9.8−3.9+11.8)nb (<27.5nb at 90% C.L.) or (425.6−43.7+42.9)nb.

Measurement of the total cross section from elastic scattering in pp collisions at [formula omitted] with the ATLAS detector

A measurement of the total pp cross section at the LHC at s=7 TeV is presented. In a special run with high-β⋆ beam optics, an integrated luminosity of 80 μb−1 was accumulated in order to measure the differential elastic cross section as a function of the Mandelstam momentum transfer variable t. The measurement is performed with the ALFA sub-detector of ATLAS. Using a fit to the differential elastic cross section in the |t| range from 0.01 GeV2 to 0.1 GeV2 to extrapolate to |t|→0, the total cross section, σtot(pp→X), is measured via the optical theorem to be:σtot(pp→X)=95.35±0.38(stat.)±1.25(exp.)±0.37(extr.)mb, where the first error is statistical, the second accounts for all experimental systematic uncertainties and the last is related to uncertainties in the extrapolation to |t|→0. In addition, the slope of the elastic cross section at small |t| is determined to be B=19.73±0.14(stat.)±0.26(syst.) GeV−2.

Production of W and Z bosons in heavy-ion collisions with CMS

Abstract Weak bosons do not participate in the strong interaction, and thus constitute clean probes of the initial state of nucleus–nucleus collisions. The comparison of their production cross sections in pp and in nuclear collisions provides constraints on the nuclear parton distribution functions. Despite the low production cross section of weak bosons, compared to other nuclear processes, the relatively clean signal of their leptonic decay channels allows their detection and reconstruction. A first analysis of PbPb data has confirmed the medium-blind characteristic of the electroweak bosons. This paper reports measurements of Z and W bosons, produced in PbPb and pp collisions at nucleon–nucleon centre of mass energy s NN = 2.76 TeV with the CMS detector. The Z boson yield and the nuclear modification factor ( R AA ) corresponding to an integrated luminosity of 150 μb − 1 are presented, as a function of the centrality, of the Z rapidity and p T , both in the muonic and electronic channels. Event centrality and muon pseudorapidity dependencies of the W production yields are presented separately for W + and W − .

Measurements of b-jet nuclear modification factors in pPb and PbPb collisions with CMS

We present measurements of the nuclear modification factors RAA and RpA(PYTHIA) of b jets in lead-lead and proton-lead collisions, respectively, using the CMS detector. Jets from b-quark fragmentations are found by exploiting the long lifetime of the b-quark through tagging methods using distributions of the secondary vertex displacement. From these, b-jet cross-sections are calculated and compared to the pp cross-section from the 2.76 TeV pp data collected in 2013 and to a PYTHIA simulation at 5.02 TeV, where these center-of-mass energies correspond to those of the PbPb and pPb data. We observe significant suppression for b jets in PbPb, and a RpA(PYTHIA) value consistent with unity for b jets in pPb. Results from both collision species show remarkable correspondence with inclusive-jet suppression measurements, indicating that mass-dependent energy-loss effects are negligible at pT values greater than around 50 GeV/c. We use 150 inverse {\mu}b of lead-lead data and 35 inverse nb of proton-lead data collected at the LHC.

Pp interaction at very high energies in cosmic ray experiments

An analysis of p-air cross section data from extensive air shower measurements is presented, based on an analytical representation of the pp scattering amplitudes that describes with high precision all available accelerator data at ISR, SPS and LHC energies. The theoretical basis of the representation, together with the very smooth energy dependence of parameters controlled by unitarity and dispersion relations, permits reliable extrapolation to high energy cosmic ray (CR) and asymptotic energy ranges. Calculations of based on Glauber formalism are made using the input values of the quantities , , BI and BR at high energies, with attention given to the independence of the slope parameters, with . The influence of contributions of diffractive intermediate states, according to Good–Walker formalism, is examined. The comparison with CR data is very satisfactory in the whole pp energy interval from 1 to 100 TeV. High energy asymptotic behaviour of cross sections is investigated in view of the geometric scaling property of the amplitudes. The observed energy dependence of the ratio between p-air and pp cross sections in the data is shown to be related to the nature of the pp cross section at high energies, that does not agree with the black disk image.

Study of [formula omitted] in the vicinity of [formula omitted

Using 2917 pb−1 of data accumulated at 3.773 GeV, 44.5 pb−1 of data accumulated at 3.65 GeV and data accumulated during a ψ(3770) line-shape scan with the BESIII detector, the reaction e+e−→pp¯ is studied considering a possible interference between resonant and continuum amplitudes. The cross section of e+e−→ψ(3770)→pp¯, σ(e+e−→ψ(3770)→pp¯), is found to have two solutions, determined to be (0.059−0.020+0.070±0.012) pb with the phase angle ϕ=(255.8−26.6+39.0±4.8)° (<0.166 pb at the 90% confidence level), or σ(e+e−→ψ(3770)→pp¯)=(2.57−0.13+0.12±0.12) pb with ϕ=(266.9−6.3+6.1±0.9)° both of which agree with a destructive interference. Using the obtained cross section of ψ(3770)→pp¯, the cross section of pp¯→ψ(3770), which is useful information for the future PANDA experiment, is estimated to be either (9.8−3.9+11.8) nb (<27.5 nb at 90% C.L.) or (425.6−43.7+42.9) nb.

Modeling $\bar{p}p$ and recent LHC pp total cross-sections

New technique is presented for modeling total cross-section of both pp and [Formula: see text] collisions from low to ultra high energy regions using an efficient artificial neural network (ANN). We have used the input (center-of-mass energy, [Formula: see text], and type of particle P) and output (total cross-section σ tot ) data to build a prediction model by ANN. The neural network has been trained to produce a function that studies the dependence of σ tot on [Formula: see text] and P. The trained ANN model shows a good performance in matching the trained distributions, predicts cross-sections that are not presented in the training set. The general trend of the predicted values shows a good agreement with the recent Large Hadron Collider (LHC) measurements, where the total cross-section at [Formula: see text] and 8 TeV are measured to be 98.6 mb and 101.7 mb, respectively. The predicted values of the total cross-section at [Formula: see text] and 14 TeV are found to be 105.8 mb and 111.7 mb, respectively. Those predictions are in good agreement with Block, Cudell and Nakamura.