Cross Section For Pp Research Articles

Measurement of the cross section for production of $ b\overline b X $ decaying to muons in pp collisions at $ \sqrt {s} = 7 $ TeV

Abstract A measurement of the inclusive cross section for the process pp → $ {\text{b}}\overline {\text{b}} {\text{X}} $ → μμX′ at $ \sqrt {s} = 7 $ TeV is presented, based on a data sample corresponding to an integrated luminosity of 27.9 pb−1 collected by the CMS experiment at the LHC. By selecting pairs of muons each with pseudorapidity |η| < 2.1, the value σ(pp → $ {\text{b}}\overline {\text{b}} {\text{X}} $ → μμX′) = 26.4 ± 0.1 (stat.) ±2.4 (syst.) ±1.1 (lumi.) nb is obtained for muons with transverse momentum p T > 4 GeV, and 5.12 ± 0.03 (stat.) ± 0.48 (syst.) ± 0.20 (lumi.) nb for p T > 6 GeV. These results are compared to QCD predictions at leading and next-to-leading orders.

Search for lepton flavour violation in the eμ continuum with the ATLAS detector in [Formula: see text]pp collisions at the LHC.

This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark (tilde{t}) in the e±μ∓ continuum using 2.1 fb−1 of data collected by the ATLAS detector in sqrt{s}=7~mbox{TeV}pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 % C.L. are calculated as a function of the scalar top mass (m_{tilde{t}}). The upper limits on the production cross section for pp→eμX, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m_{tilde{t}}=95~mbox{GeV} to 30 fb for m_{tilde{t}}=1000~mbox{GeV}.

Search for a Dark Matter Candidate Produced in Association with a Single Top Quark inpp¯Collisions ats=1.96 TeV

We report a new search for dark matter in a data sample of an integrated luminosity of 7.7 fb-1 of Tevatron pp[over ¯] collisions at √[s]=1.96 TeV, collected by the CDF II detector. We search for production of a dark-matter candidate, D, in association with a single top quark. We consider the hadronic decay mode of the top quark exclusively, yielding a final state of three jets with missing transverse energy. The data are consistent with the standard model; we thus set 95% confidence level upper limits on the cross section of the process pp[over ¯]→t+D as a function of the mass of the dark-matter candidate. The limits are approximately 0.5 pb for a dark-matter particle with mass in the range of 0-150 GeV/c2.

Measurement ofZZProduction in Leptonic Final States atsof 1.96 TeV at CDF

In this Letter, we present a precise measurement of the total ZZ production cross section in pp collisions at sqrt[s]=1.96 TeV, using data collected with the CDF II detector corresponding to an integrated luminosity of approximately 6 fb(-1). The result is obtained by combining separate measurements in the four-charged (ℓℓℓ' ℓ') and two-charged-lepton and two-neutral-lepton (ℓℓνν) decay modes of the Z boson pair. The combined measured cross section for pp → ZZ is 1.64(-0.38)(+0.44) pb. This is the most precise measurement of the ZZ production cross section in 1.96 TeV pp collisions to date.

Observation of ExclusiveγγProduction inpp¯Collisions ats=1.96 TeV

We have observed exclusive γγ production in proton-antiproton collisions at √s=1.96 TeV, using data from 1.11±0.07 fb(-1) integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromagnetic showers, each with transverse energy E(T)>2.5 GeV and pseudorapidity |η|<1.0, with no other particles detected in -7.4<η<+7.4. The two showers have similar E(T) and azimuthal angle separation Δφ~π; 34 events have two charged particle tracks, consistent with the QED process pp¯→p+e(+)e(-)+p¯ by two-photon exchange, while 43 events have no charged tracks. The number of these events that are exclusive π(0)π(0) is consistent with zero and is <15 at 95% C.L. The cross section for pp¯→p+γγ+p¯ with |η(γ)|<1.0 and E(T)(γ)>2.5 GeV is 2.48(-0.35)(+0.40)(stat)(-0.51)(+0.40)(syst) pb.

Kaon pair production in proton-proton collisions at COSY-ANKE

The near-threshold production of kaon-pairs has been investigated in proton-proton collisions at Cooler Synchrotron (COSY)at Forschungszentrum Jülich. In the pp → ppK+K− reaction, the invariant mass distributions of K−p, K−pp, and K+K− indicate the presence of both K−p and K+K− final state interactions. Total cross sections for pp → ppϕ reaction have been determined at excess energies ε of 18.5, 34.5, and 76 MeV. The differential spectra at an excess energy of 18.5 MeV exhibit a clear s-wave dominance, while the high statics data at an excess energy of 76 MeV shows that higher partial waves represent the majority of the pp → ppϕ total cross section, whose energy dependence would then seem to require some s-wave ϕp enhancement near threshold.

Measurement of Inelastic, Diffractive and Exclusive Processes in pp Collisions with CMS

A measurement of the total, inelastic pp cross section at 7 TeV, based on the observation of pile-up events, is presented. Measurements of soft and hard diffractive processes obtained with the CMS detector at various centre-of-mass energies are presented and compared with the PYTHIA6, PHOJET and PYTHIA8 Monte Carlo generators. The ratio of diffractive to inclusive jet production is obtained and the rapidity gap survival probability is estimated from the comparison of data to predictions of the POMPYT generator. A measurement of exclusive production of muon pairs in pp collisions at √ s = 7 TeV is also presented. Single differential cross sections are obtained as function of the dimuon transverse momentum, invariant mass and acoplanarity for dimuon pairs with an invariant mass above 11 GeV. Data are compared to predictions of the LPAIR Monte Carlo model.

Nuclear Geometry and Number of Collisions: Glauber Model and Beyond

The number of collisions, which is the factor used to normalize the pA over pp cross section ratio for hard processes, is calculated within: (i) the Glauber single channel approximation; (ii) adding the Gribov inelastic shadowing corrections; (iii) adding the effects of the short-range NN correlations. The largest effect is found to be related to inclusion or exclusion of the diffractive channels in the trigger.

Measurement of thett¯production cross section inppcollisions at 7 TeV inlepton+jetsevents usingb-quark jet identification

A new measurement of the inclusive production cross section for pp to t t-bar is performed at a center-of-mass energy of 7 TeV using data collected by the CMS experiment at the LHC. The analysis uses a data sample corresponding to an integrated luminosity of 36 inverse picobarns, and is based on the final state with one isolated, high transverse momentum muon or electron, missing transverse energy, and hadronic jets. The ttbar content of the selected events is enhanced by requiring the presence of at least one jet consistent with b-quark hadronization. The measured cross section is 150 +/- 9 (stat.) +/- 17 syst.) +/- 6 (lumi.) pb and is in agreement with higher-order QCD calculations. The combination of this measurement with a previous CMS result based on dileptons gives 154 +/- 17 (stat.+syst.) +/- 6 (lumi.) pb.

The anomalous top quark coupling tqg and tW production at the LHC

Many new physics models beyond the standard model (SM) can give rise to the large anomalous top couplings tqg (q=u and c). We focus our attention on these couplings induced by the topcolor-assisted technicolor (TC2) model and the littlest Higgs model with T-parity (called LHT model), and consider their contributions to the production cross section and the charge asymmetry for tW production at the LHC. We find that the anomalous top coupling tqg induced by these two kinds of new physics models can indeed generate sizable charge asymmetry. The correction effects of the LHT model on the production cross sections of the processes pp→tW−+X and pp→t¯W++X are significant large, which might be detected at the LHC.

The Recent Absolute Total np and pp Cross Section Determinations: Quality of Data Description and Prediction of Experimental Observables

The 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 the most recent ENDF/B-VII.0 and JENDL-3.3 data files, and the Nijmegen PWA. Systematic deviations from the ENDF/B-VII.0 and JENDL-3.3 evaluations are found to exist in the low-energy region. Comparison of the np evaluation with the result of most recent np total and differential cross section measurements will be discussed. Results of those measurements were not used in the evaluation database. A comparison was done to check a quality of evaluation and its capabilities to predict experimental observables. Excellent agreement was found between the new experimental data and our PWA predictions.

Searches for the technicolor signatures via gg → W±πt∓ at the Large Hadron Collider

In this paper, we calculate the production of a charged top pion in association with a W boson via gg fusion at CERN's Large Hadron Collider in the context of the topcolor assisted technicolor model. We find that the total cross section of pp → gg → W±πt∓ is several dozen femtobarns with reasonable values of the parameters, and the total cross section of pp → W±πt∓ can reach a few hundred femtobarns when we consider the sum of the contributions of these two parton subprocesses, gg → W±πt∓ and bb̄ → W±πt∓.

Development of radiation hard edgeless detectors with current terminating structure on p-type silicon

Abstract The development of edgeless Si detectors was stimulated by the tasks of the total pp cross-section study in the TOTEM experiment at the Large Hadron Collider at CERN. For this, the dead region at the detector diced side should be reduced below 50 μm. This requirement is successfully realized in edgeless Si detectors with current terminating structure (CTS), which are now operating at LHC. The development of the experiment and future LHC upgrade need the elaboration of radiation hard version of edgeless Si detectors. The current investigation represents an extension in understanding on edgeless detectors operation and development of a new issue – edgeless detectors with CTS on p-type Si.

Associated Production of a Neutral Top-Higgs with Top Quark Pairs at the LHC within the TC2 model

Within the context of the topcolor-assisted technicolor (TC2) model we investigate the associated production of the neutral top-higgs ht0 with a pair of top quarks, i.e. pp → tt̄ht0 at the Large Hadron Collider (LHC), which proceeds through the partonic processes qq̄ → tt̄ht0 and gg → tt̄ht0. We calculate the production rate and show the distributions of the transverse momenta of ht0. It is found that the cross section of pp → tt̄ht0 can reach a few hundred fb in the most part of the allowed parameter space and even a few tens of pb for the light top-higgs. Due to the large cross section of tt̄ht0 production and the top-charm decay mode of ht0 for mht0 < 2mt, the process pp → tt̄ht0 can play an important role in the probe of neutral top-higgs and the test of the TC2 model.

Multiple parton interactions and forward double pion production inppanddAscattering

We estimate the contributions by double-parton interactions to the cross sections for pp->pi^0 pi^0 X and dA->pi^0 pi^0 X at RHIC. We find that such contributions become important at large forward rapidities of the produced pions. This is in particular the case for dA scattering, where they strongly enhance the azimuthal-angular independent "pedestal" component of the cross section, providing a natural explanation of this feature of the RHIC dA data. We argue that the discussed processes open a window to studies of double quark distributions in nucleons. We also briefly address the roles of shadowing and energy loss in dA scattering, which we show to affect the double-inclusive pion cross section much more strongly than the single-inclusive one. We discuss the implications of our results for the interpretation of pion azimuthal correlations.

STUDIES OF OPEN CHARM AND CHARMONIUM PRODUCTION AT LHCb

We present recent results from charmonium and open charm production at the LHCb experiment at CERN, Geneva. We concentrate on studies for the measurement of the cross section pp → J/ψX in its decay channel with two muons, showing the agreement of the simulation with the data in few key distributions. We also show the reconstructed modes of D0 → K-π+, D0 → K-π+π0, [Formula: see text] and [Formula: see text] and their prospects.

Forward physics at the LHC: detecting elastic pp scattering by radiative photons

Photon bremsstrahlung is proposed to be used to identify elastic proton-proton interactions at the LHC. In addition to a measurement of the elastic pp cross section (assuming that the elastic slope is known), the bremsstrahlung photons will allow the evaluation of the total pp cross section, luminosity and to align the Zero Degree Calorimeters (ZDCs).

The measurement of the [formula omitted] reaction near threshold

It is shown that a recent extraction of the total cross section for pp→K+nΣ+ from inclusive K+ production data by the HIRES Collaboration [Phys. Lett. B 692 (2010) 10] is in conflict with experimental data on the exclusive pp→K+pΛ reaction. The HIRES result may be interpreted as an upper bound, which is not inconsistent with the much lower values that already exist in the literature.

Effective four-fermion operators in top physics: A roadmap

We write down a minimal basis for dimension-six gauge-invariant four-fermion operators, with some operator replacements with respect to previous ones which make it simpler for calculations. Using this basis we classify all four-fermion operator contributions involving one or two top quarks. Taking into account the different fermion chiralities, possible colour contractions and independent flavour combinations, a total number of 572 gauge-invariant operators are involved. We apply this to calculate all three-body top decay widths t → d k u i d ¯ j , t → d k e i + ν j , t → u k u i u ¯ j , t → u k e j + e i − , t → u k ν ¯ j ν i (with i , j , k generation indices) mediated by dimension-six four-fermion operators, including the interference with the Standard Model amplitudes when present. All single top production cross sections in pp, p p ¯ and e + e − collisions are calculated as well, namely u i d k → d j t , d ¯ j d k → u ¯ i t , u i d ¯ j → d ¯ k t , u i u k → u j t , u i u ¯ j → u ¯ k t , e + e − → u ¯ k t and the charge conjugate processes. We also compute all top pair production cross sections, u ¯ i u j → t t ¯ , d ¯ i d j → t t ¯ , u i u j → t t and e + e − → t t ¯ . Our results are completely general, without assuming any particular relation among effective operator coefficients.

Modeling pion and proton total cross-sections at LHC

To settle the question whether the growth with energy is universal for different hadronic total cross-sections, we present results from theoretical models for πp, and (pp, pp¯) total cross-sections. We show that present and planned experiments at LHC can differentiate between different models, all of which are consistent with presently available (lower energy) data. This study is also relevant for the analysis of those very high energy cosmic ray data which require reliable πp total cross-sections as seeds. A preliminary study of the total ππ cross-sections is also made.