Central exclusive and semiexclusive production of $π^+π^-$ pairs is measured with the CMS detector in proton-proton collisions at the LHC at center-of-mass energies of 5.02 and 13 TeV. The theoretical description of these nonperturbative processes, which have not yet been measured in detail at the LHC, poses a significant challenge to models. The two pions are measured and identified in the CMS silicon tracker based on specific energy loss, whereas the absence of other particles is ensured by calorimeter information. The total and differential cross sections of exclusive and semiexclusive central $π^+π^-$ production are measured as functions of invariant mass, transverse momentum, and rapidity of the $π^+π^-$ system in the fiducial region defined as transverse momentum $p_\mathrm{T}(π)$ $>$ 0.2 GeV and pseudorapidity $|η(π)|$ $<$ 2.4. The production cross sections for the four resonant channels f$_0(500)$, $ρ^0(770)$, f$_0(980)$, and f$_2(1270)$ are extracted using a simple model. These results represent the first measurement of this process at the LHC collision energies of 5.02 and 13 TeV.
We report new results from CDF on single-diffractive dijet and W/Z production, and on exclusive dijet, diphoton, and dilepton production in proton-antiproton collisions at sqrt{s}=1.96 TeV at the Fermilab Tevatron. The measured exclusive dijet and diphoton cross sections provide a test of theoretical predictions for exclusive Higgs production at the LHC.
Results from studies on exclusive production of electron-position pair, di-photon, and di-jet production at CDF in proton-antiproton collisions at the Fermilab Tevatron are presented. The first observation and cross section measurements of exclusive e+e- and di-jet production in hadron-hadron collisions are emphasized.
In CDF we have observed several exclusive processes: 2-photon --> e+e- and --> mu+mu-, photon+pomeron --> J/psi and psi(2S), and pomeron+pomeron --> chi_c. The cross sections agree with QED, HERA photoproduction data, and theoretical estimates of gg --> chi_c with another gluon exchanged to screen the color. This observation of exclusive chi_c, together with earlier observations of exclusive dijets and exclusive 2-photon candidates, support some theoretical predictions for p+p --> p+H+p at the LHC. Exclusive dileptons offer the best means of precisely calibrating forward proton spectrometers.
A search for exclusive or semi-exclusive photon pair production, pp to p(*) + photon pair + p(*) (where p(*) stands for a diffractively-dissociated proton), and the observation of exclusive and semi-exclusive electron pair production, pp to p(*) + ee + p(*), in proton-proton collisions at sqrt(s) = 7 TeV, are presented. The analysis is based on a data sample corresponding to an integrated luminosity of 36 inverse picobarns recorded by the CMS experiment at the LHC at low instantaneous luminosities. Candidate photon pair or electron pair events are selected by requiring the presence of two phot…
We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the D0 experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is $2 \times 10^{-5}$, corresponding to a 4.1 standard deviation significance.
We present the first observation and cross section measurement of exclusive dijet production in pbar-p interactions, pbar + p --> pbar + dijet + p. Using a data sample of 310 pb-1 collected by the Run II Collider Detector at Fermilab at sqrt{s}=1.96 TeV, exclusive cross sections for events with two jets of transverse energy ET >= 10 GeV have been measured as a function of minimum ET(jet). The exclusive signal is extracted from fits to data distributions based on Monte Carlo simulations of expected dijet signal and background shapes. The simulated background distribution shapes are checked in a…
The Collider Detector at Fermilab, CDF, observed for the first time in hadron-hadron collisions photon-photon to e+e- and mu+mu-, photon-pomeron to J/psi and psi(2S), and pomeron-pomeron to photon+photon and to chi_c. Exclusive pi+pi- production by double pomeron exchange was also measured at p+pbar CM energies 900 GeV and 1960 GeV, showing f0 and f2 resonance structures.
We present a search for exclusive Z boson production in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using the CDF II detector at Fermilab. We observe no exclusive Z->ll candidates and place the first upper limit on the exclusive Z cross section in hadron collisions, sigma(exclu) < 0.96 pb at 95% confidence level. In addition, we observe eight candidate exclusive dilepton events from the quantum electrodynamic process ppbar->gammagamma->p+ll+pbar, and measure the cross section for M(ll) > 40 GeV/c2 and |eta(l)| < 4 to be sigma = 0.24^{+0.13}_{-0.10} pb, which is the first measurement fo…
A measurement is presented of the exclusive and semi-exclusive production of charged pion pairs in proton-proton collisions, pp to p(p*) + $π^+π^-$ + p(p*) here the $π^+π^-$ pair is emitted at central rapidities, and the scattered protons stay intact (p) or diffractively dissociate (p*) without detection. The measurement is performed with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 450 inverse microbarns collected at a center-of-mass energy of 7 TeV. The dipion cross section, measured for single-pion transverse momentum pt >0.2 GeV and rapidity…
The LHCb collaboration has measured central exclusive production of $J/ψ$, $ψ(2S)$, and $Υ$ mesons as well as $J/ψJ/ψ$, $J/ψψ(2S)$, $ψ(2S)ψ(2S)$, and $χ_cχ_c$ meson pairs in proton-proton collisions. The analyses of $Υ$ and charmonium pairs are performed at the centre-of-mass energies of 7 TeV and 8 TeV, and those of $J/ψ$ and $ψ(2S)$ are done at 7 TeV and 13 TeV. The analysis at 13 TeV involves the use of new shower counters. These allow a reduction in the background by vetoing events with activity in an extended region in rapidity. The measurements of central exclusive production at LHCb are…
A search for exclusive or quasi-exclusive gamma gamma to W+W- production, via pp to p(*) W+W- p(*) to p(*) mu+/- e-/+ at sqrt(s) = 8 TeV, is reported using data corresponding to an integrated luminosity of 19.7 inverse femtobarns. Events are selected by requiring the presence of an electron-muon pair with large transverse momentum pt(mu+/- e-/+) > 30 GeV, and no associated charged particles detected from the same vertex. The 8 TeV results are combined with the previous 7 TeV results (obtained for 5.05 inverse femtobarns of data). In the signal region, 13 (2) events are observed over an expecte…
Searches for exclusively produced $W$ boson pairs in the process $pp(γγ) \rightarrow pW^+W^-p$ and exclusively produced Higgs boson in the process $pp(gg) \rightarrow pHp$ have been performed using $e^{\pm}μ^{\mp}$ final states. These measurements use 20.2 fb$^{-1}$ of $pp$ collisions collected by the ATLAS experiment at a center-of-mass energy $\sqrt{s}=8$ TeV at the LHC. Exclusive production of $W^+W^-$ consistent with the Standard Model prediction is found with 3.0$σ$ significance. The exclusive $W^+W^-$ production cross-section is determined to be $σ(γγ\rightarrow W^{+}W^{-}\rightarrow e^{…
By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt{s}=3.773$ GeV and 6.5 pb$^{-1}$ taken at $\sqrt{s}=3.650$ GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in $e^+e^-$ annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for $ψ(3770)$ decay to these final states at 90% C.L.
This article contains a summary of the recent results in diffractive physics at the Tevatron. Results from the CDF diffraction program include the single diffractive to non-diffractive ratio in dijet events, observation of exclusive $e^+e^-$ production via two-photon exchange, hints of exclusive $γγ$ production via Double Pomeron Exchange (DPE), and the observation of exclusive dijet production via DPE. A summary of the current plans for the DØ diffractive physics program is also presented.
The production of exclusive $γγ\rightarrow μ^+ μ^-$ events in proton--proton collisions at a centre-of-mass energy of 13 TeV is measured with the ATLAS detector at the LHC, using data corresponding to an integrated luminosity of 3.2 fb$^{-1}$. The measurement is performed for a dimuon invariant mass of 12 GeV $<m_{μ^+μ^-}<$ 70 GeV. The integrated cross-section is determined within a fiducial acceptance region of the ATLAS detector and differential cross-sections are measured as a function of the dimuon invariant mass. The results are compared to theoretical predictions that include corrections…
The exclusive photoproduction of $Υ$(1S), $Υ$(2S) and $Υ$(3S) mesons is studied in their leptonic ($μ^{+}μ^{-}$) decay modes, in ultraperipheral pPb collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The data was recorded by the CMS experiment corresponding to an integrated luminosity of $32.6$ nb$^{-1}$. The differential cross-section for $Υ$(n) states (n=1,2,3), has been measured as a function of transverse momentum squared $p_{T}^{2}$, and rapidity $y$. The $Υ$(1S) photoproduction cross-section is extracted in the region $|y|<2.2$ as a function of the photon-proton centre-of-mass energies $W_{γp}$, …
The search for central exclusive production of muon pairs is performed using the LHCb data acquired on 2011 ($\sqrt{s} = 7$ TeV) and 2012 ($\sqrt{s} = 8$ TeV). Preliminary measurements of cross section using these samples are showed and a first comparison with theoretical previews is presented.
We measure the Lambda_b^0 lifetime in the fully reconstructed decay Lambda_b^0 -> J/psi Lambda^0 using 10.4 fb^-1 of ppbar collisions collected with the D0 detector at sqrt(s)=1.96 TeV. The lifetime of the topologically similar decay channel B^0 -> J/psi K^0_S is also measured. We obtain tau(Lambda_b^0) = 1.303 +- 0.075 (stat.) +- 0.035 (syst.) ps and tau(B^0) = 1.508 +- 0.025 (stat.) +- 0.043 (syst.) ps. Using these measurements, we determine the lifetime ratio of tau(Lambda_b^0)/tau(B^0) = 0.864 +- 0.052 (stat.) +- 0.033 (syst.).
A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at sqrt(s)= 7 TeV, pp to p mu^+ mu^- p, is reported using data corresponding to an integrated luminosity of 40 inverse picobarns. For muon pairs with invariant mass greater than 11.5 GeV, transverse momentum pT(mu) > 4 GeV and pseudorapidity |eta(mu)| < 2.1, a fit to the dimuon pt(mu^+ mu^-) distribution results in a measured cross section of sigma(pp to p mu^+ mu^- p) = 3.38 [+0.58 -0.55] (stat.) +/- 0.16 (syst.) +/- 0.14 (lumi.) pb, consistent with the theoretical prediction evaluated with the even…
A search for exclusive or quasi-exclusive W(+)W(-) production by photon-photon interactions, pp to p(*)W(+)W(-)p(*), at sqrt(s) = 7 TeV is reported using data collected by the CMS detector with an integrated luminosity of 5.05 inverse femtobarns. Events are selected by requiring a mu(+/-)e(-/+) vertex with no additional associated charged tracks and dilepton transverse momentum pt(mu(+/-)e(-/+)) > 30 GeV. Two events passing all selection requirements are observed in the data, compared to a standard model expectation of 2.2 +/- 0.4 signal events with 0.84 +/- 0.15 background. The tail of the di…
A measurement is presented for the energy flow of minimum bias events in the forward region (3.15 <|η|< 4.9, where ηis the pseudorapidity) of the CMS detector at the LHC for center-of-mass energies sqrt(s) = 0.9 TeV, 2.36 TeV and 7 TeV. The measurement is compared to Monte Carlo simulations, which use a model of multiparton interactions for the underlying event. In addition, production of forward jets was studied for the very first pp collisions at sqrt(s) = 0.9 TeV at LHC.
The relative rates of single- and double- diffractive processes were measured with the ALICE detector by studying properties of gaps in the pseudorapidity distribution of particles produced in proton-proton collisions at $\sqrt{s}$ = 0.9 TeV, 2.76 TeV and 7 TeV. ALICE triggering efficiencies are determined for various classes of events, using a detector simulation validated with data on inclusive particle production. Cross-sections are determined using van der Meer scans to measure beam properties and obtain a measurement of the luminosity.
By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt s= 3.773$ GeV and of 6.5 pb$^{-1}$ taken at $\sqrt s= 3.650$ GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for the exclusive light hadron final states of $K_S^0K^-π^+$, $K_S^0K^-π^+π^0$, $K_S^0K^-π^+π^+π^-$, $K_S^0K^-π^+π^+π^-π^0$, $K_S^0K^-π^+π^+π^+π^-π^-$ and $K_S^0K^-π^+π^0π^0$ produced in $e^+ e^-$ annihilation at the two energy points. We set the upper limits on the observed cross sections and the branching fractions for $ψ(3770)$ decay to these final states at 90% C.L..
The WZ production cross section is measured by the CMS experiment at the CERN LHC in proton-proton collision data samples corresponding to integrated luminosities of 4.9 inverse femtobarns collected at sqrt(s)= 7 TeV, and 19.6 inverse femtobarns at sqrt(s)= 8 TeV. The measurements are performed using the fully-leptonic WZ decay modes with electrons and muons in the final state. The measured cross sections for 71 < m[Z] < 111 GeV are sigma(pp to WZ; sqrt(s)= 7 TeV) = 20.14 +/- 1.32 (stat) +/- 1.13 (syst) +/- 0.44 (lumi) pb and sigma(pp to WZ; sqrt(s)= 8 TeV) = 24.09 +/- 0.87 (stat) +/- 1.62 (sy…
Rapidity distributions are presented for events containing either a Z boson or a photon with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at sqrt(s) = 7 TeV, correspond to an integrated luminosity of 5.0 inverse femtobarns. The individual rapidity distributions of the boson and the jet are consistent within 5% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show discrepancies with CMS data. In particular, next-to-leading-order QCD calcula…
An updated search for heavy narrow resonances decaying to muon or electron pairs using the CMS detector is presented. Data samples from pp collisions at sqrt(s) = 7 TeV and 8 TeV at the LHC, with integrated luminosities of up to 5.3 and 4.1 inverse femtobarns, respectively, are combined. No evidence for a heavy narrow resonance is observed. The analysis of the combined data sets excludes, at 95% confidence level, a Sequential Standard Model Z'[SSM] resonance lighter than 2590 GeV, a superstring-inspired Z'[psi] lighter than 2260 GeV, and Kaluza-Klein gravitons lighter than 2390 (2030) GeV, ass…
A brief survey of the results on diboson production at the Tevatron is presented. Measured cross sections for $Wγ$, $Zγ$, $WW$, and limits on WZ/ZZ are summarized.
A measurement of the underlying activity in scattering processes with a hard scale in the several GeV region is performed in proton-proton collisions at sqrt(s) = 0.9 and 7 TeV, using data collected by the CMS experiment at the LHC. The production of charged particles with pseudorapidity |eta| < 2 and transverse momentum pT > 0.5 GeV/c is studied in the azimuthal region transverse to that of the leading set of charged particles forming a track-jet. A significant growth of the average multiplicity and scalar-pT sum of the particles in the transverse region is observed with increasing pT of the …
Prompt photon production results by the CDF and D\OCollaborations in the Tevatron Run II at a center of mass energy of $\sqrt{s}$=1.96 TeV are presented. Cross sections for central isolated photons, photon+jet production and photons produced in association with a heavy flavor quark are reported. The measurements are compared to Next-to-Leading order perturbative QCD predictions.
Latest jet results from the Tevatron are presented in this conference note. These are namely: new results on central inclusive jet production using both cone and $k_T$ algorithms, measurement of decorrelation in azimuthal angle between the two jets with the highest transverse momenta, and study of jet shapes. Results are based on data collected in $\mathrm{p}\bar{\mathrm{p}}$ collisions at $\sqrt{s}=1.96 \mathrm{TeV}$ in the years 2001-2004. Depending on the analysis, integrated luminosity of the sample was up to $378 \mathrm{pb}^{-1}$.
The exclusive photoproduction of $Υ$(nS) meson states from protons, $γ$p $ \toΥ$(nS)p (with n = 1, 2, 3), is studied in ultraperipheral pPb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. The measurement is performed using the $Υ$(nS) $\to μ^+μ^-$ decay mode, with data collected by the CMS experiment corresponding to an integrated luminosity of 32.6 nb$^{-1}$. Differential cross sections as functions of the $Υ$(nS) transverse momentum squared $p_\mathrm{T}^2$, and rapidity $y$, are presented. The $Υ$(1S) photoproduction cross section is extracted in…
Results of the measurement of the $π$, K, p transverse momentum ($p_{\mathrm{t}}$) spectra at mid-rapidity in proton-proton collisions at $\sqrt{s} = 7$ TeV are presented. Particle identification was performed using the energy loss signal in the Inner Tracking System (ITS) and the Time Projection Chamber (TPC), while information from the Time-of-Flight (TOF) detector was used to identify particles at higher transverse momentum. From the spectra at $\sqrt{s} = 7$ TeV the mean transverse momentum ($<p_{\mathrm{t}}>$) and particle ratios were extracted and compared to results obtained for collisi…
By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to π^+π^-π^0π^0$, $K^+K^-π^0π^0$, $2(π^+π^-π^0)$, $K^+K^-π^+π^-π^0π^0$ and $3(π^+π^-)π^0π^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $ψ(3770)$ decay into these final states at 90% C.L..
Proceeding for LHCP2017 conference. Referencing the ATLAS publication note: http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2017-005/
Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.
The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy $\sqrt{s} = 7$ TeV, were measured in the central pseudorapidity region |$η$| < 1. Comparisons are made with previous measurements at $\sqrt{s}$ = 0.9 TeV and 2.36 TeV. At $\sqrt{s}$ = 7 TeV, for events with at least one charged particle in |$η$| < 1, we obtain dNch/deta = 6.01 $\pm$ 0.01 (stat.) $^{+0.20}_{-0.12}$ (syst.). This corresponds to an increase of 57.6% $\pm$ 0.4% (stat.) $^{+3.6}_{-1.8}$% (syst.) relative to collisions at 0.9 TeV, …
The availability at the LHC of the largest collision energy in pp collisions allows a significant advance in the measurement of $J/ψ$ production as function of event multiplicity. The interesting relative increase observed with data at the LHC at $\sqrt{s} = 7\,\mathrm{TeV}$ and at RHIC at $\sqrt{s} = 0.2\,\mathrm{TeV}$ is studied now at unprecedented multiplicities at $\sqrt{s} = 13\,\mathrm{TeV}$. The measurement at mid-rapidity in the dielectron channel with ALICE is presented and discussed in comparison to predictions from available theoretical models and to data at lower energies.
The inclusive jet cross-section has been measured in proton-proton collisions at sqrt(s)=2.76 TeV in a dataset corresponding to an integrated luminosity of 0.20pb-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. Jets are identified using the anti-kt algorithm with two radius parameters of 0.4 and 0.6. The inclusive jet double-differential cross-section is presented as a function of the jet transverse momentum pT and jet rapidity y, covering a range of 20 <= pT < 430 GeV and |y| < 4.4. The ratio of the cross-section to the inclusive jet cross-section measurement at sqrt…
Searches for the exclusive decays of the Higgs and $Z$ bosons into a $J/ψ$, $ψ(2S)$, or $Υ(nS)$ ($n=1,2,3$) meson and a photon are performed with a $pp$ collision data sample corresponding to an integrated luminosity of 36.1 fb$^{-1}$ collected at $\sqrt{s}=13$ TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above the expected backgrounds, and 95% confidence-level upper limits on the branching fractions of the Higgs boson decays to $J/ψγ$, $ψ(2S)γ$, and $Υ(nS)γ$ of $3.5\times10^{-4}$, $2.0\times10^{-3}$, and $(4.9,5.9,5.7)\times10^{-4}…
The cross sections for the reactions $e^+e^- \to ϕη, \quad ϕη', \quad ρη, \quad ρη'$ have been measured using a data sample of 516 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The corresponding values of the cross sections are: $1.4 \pm 0.4 \pm 0.1$ fb $(ϕη)$, $5.3 \pm 1.1 \pm 0.4$ fb $(ϕη')$, $3.1 \pm 0.5 \pm 0.1$ fb $(ρη)$ and $3.3 \pm 0.6 \pm 0.2$ fb $(ρη')$. The energy dependence of the cross sections is presented using Belle measurements together with those of CLEO and BaBar.
The increasing size of the data recorded by the CDF and DØ experiments at the Tevatron collider at $\sqrt{s}=$ 1.96 TeV makes the diboson physics program more accessible for probes of the electroweak gauge structure in the Standard Model. Here we summarize the most recent measurements of the diboson cross sections and limits on the trilinear gauge boson couplings.
A measurement of the double-differential inclusive dijet production cross section in proton-proton collisions at \sqrt{s}= 7 TeV is presented as a function of the dijet invariant mass and jet rapidity. The data correspond to an integrated luminosity of 36 pb^{-1}, recorded with the CMS detector at the LHC in 2010. The measurement covers the dijet mass range 0.2 TeV to 3.5 TeV and jet rapidities up to |y|=2.5. It is found to be in good agreement with next-to-leading-order QCD predictions.
We present results from the ALICE experiment on the inclusive J/Psi production in pp collisions at sqrt(s)=2.76 and 7 TeV. The integrated and differential cross sections are evaluated down to pT=0 in two rapidity ranges, |y|<0.9 and 2.5<y<4, in the dielectron and dimuon decay channel respectively. The measurement at sqrt(s)=2.76 TeV, the same energy as Pb-Pb collisions, provides a crucial reference for the study of hot nuclear matter effects on J/Psi production. The J/Psi yield in pp collisions at sqrt(s)=7 TeV has also been studied as a function of the charged particle multiplicity and first …
A measurement of the double-differential inclusive dijet production cross section in proton-proton collisions at sqrt(s)=7 TeV is presented as a function of the dijet invariant mass and jet rapidity. The data correspond to an integrated luminosity of 36 inverse picobarns, recorded with the CMS detector at the LHC. The measurement covers the dijet mass range 0.2 TeV to 3.5 TeV and jet rapidities up to |y|=2.5. It is found to be in good agreement with next-to-leading-order QCD predictions.
We present data on multiple jet production for transverse energies greater than 20 GeV in pbarp collisions at sqrt(s) = 1.8 TeV. QCD calculations in the parton shower approximation (PYTHIA) and in the next-to-leading order approximation (JETRAD) show discrepancies with data for three and four-jet production. This disagreement is especially apparent in multiple jet angular and transverse momentum distributions.
The result of a search for gaugino pair production with a trilepton signature is reinterpreted in the framework of minimal supergravity (mSUGRA) with R-parity violation via leptonic lambda Yukawa couplings. The search used 95 pb^{-1} of p-barp collisions at sqrt{s}=1.8 TeV recorded by the D0 detector at the Fermilab Tevatron. A large domain of the mSUGRA parameter space is excluded for lambda_{121}, lambda_{122} > 10^{-4}.
We present measurements of the transverse momentum distribution of W and Z bosons produced in pbar p collisions at sqrt(s) = 1.8 TeV. The data were collected with the D0 detector at Fermilab during 1994-1996 Tevatron run. The results are in good agreement with theoretical predictions based on the perturbative QCD and soft gluon resummation combined calculation over the entire measured pt range p_T = 0-200 GeV/c).
The measurements of b quark, quarkonium and exotic state production performed with the ATLAS and CMS experiments at sqrt(s)=7 TeV are presented. The b-quark production cross section is measured both in inclusive and fully reconstructed B hadron decays. The results are compared with QCD expectations at tree-level and NLO.
Measurements of the angular correlations between beauty and anti-beauty hadrons produced in LHC pp collisions at $\sqrt{s}=7$ TeV are presented. These results probe for the first time the small angular separation region and show sensitivity to collinear particle emission. The results are compared with predictions based on perturbative QCD calculations at leading and next-to-leading order.
Measurements of dijet azimuthal decorrelations in pp collisions at sqrt(s) = 7 TeV using the CMS detector at the CERN LHC are presented. The analysis is based on an inclusive dijet event sample corresponding to an integrated luminosity of 2.9 inverse picobarns. The results are compared to predictions from perturbative QCD calculations and various Monte Carlo event generators. The dijet azimuthal distributions are found to be sensitive to initial-state gluon radiation.
The production of events with multiple high transverse momentum particles including charged leptons and jets is measured, using 1.04 fb-1 of proton-proton collision data recorded by the ATLAS detector during the first half of 2011 at sqrt(s) = 7 TeV. No excess beyond Standard Model expectations is observed, and upper limits on the fiducial cross sections for non-Standard Model production of these final states are set. Using models for string ball and black hole production and decay, exclusion contours are determined as a function of mass threshold and the fundamental gravity scale.
We present combined searches for the Low Mass Standard Model Higgs boson at a center-of-mass energy of $\sqrt{s}=$1.96 TeV, using up to 5 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. The major contributing processes are associated production ($WH\to lνbb$, $ZH\toννbb$, $ZH\to ll bb$). The significant improvements across the full mass range resulting from the larger data sets and improved analyses as well as future prospects are discussed.
This document gives an overview over the recent results on helicity measurement of W boson originated from top pair events. The results are obtained using data collected by the CMS detector at a center-of-mass energy of 8 TeV. The helicity measurements are confronted with the most precise theoretical predictions of the standard model.
We use a sample of diphoton + dijet events to measure the effective cross section of double parton interactions, which is found to be $σ_{\rm eff} = 19.3$ $\pm$ $1.4({\rm stat})$ $\pm$ $7.8({\rm syst})$ mb. The sample was collected by the D0 detector at the Fermilab Tevatron collider in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV and corresponds to an integrated luminosity of 8.7 fb$^{-1}$.
A measurement of the lepton charge asymmetry in inclusive pp to WX production at sqrt(s)= 7 TeV is presented based on data recorded by the CMS detector at the LHC and corresponding to an integrated luminosity of 36 inverse picobarns. This high precision measurement of the lepton charge asymmetry, performed in both the W to e nu and W to mu nu channels, provides new insights into parton distribution functions.
We report on the measurement of the central exclusive production process $pp \ \rightarrow \ pXp$ in proton-proton collisions at RHIC with the STAR detector at $\sqrt{\mathrm{s}} = 510$ GeV. At this energy, this process is dominated by a double Pomeron exchange mechanism. The tracks of the centrally produced system $X$ were reconstructed in the central detector of STAR, the Time Projection Chamber and the Time of Flight systems, and were identified using the ionization energy loss and the time of flight method. The diffractively scattered protons, moving intact inside the RHIC beam pipe after …
A search for narrow resonances in proton-proton collisions at sqrt(s) = 13 TeV is presented. The invariant mass distribution of the two leading jets is measured with the CMS detector using a data set corresponding to an integrated luminosity of 2.4 inverse femtobarns. The highest observed dijet mass is 6.1 TeV. The distribution is smooth and no evidence for resonant particles is observed. Upper limits at 95% confidence level are set on the production cross section for narrow resonances with masses above 1.5 TeV. When interpreted in the context of specific models, the limits exclude string reso…
