Search results for "Collider"
showing 10 items of 1690 documents
Search for single top quark production in pp¯ collisions at s=1.96 TeV
2005
We present a search for electroweak production of single top quarks in the s-channel and t-channel using neural networks for signal-background separation. We have analyzed 230 pb(-1) of data collected with the DO detector at the Fermilab Tevatron Collider at a center-of-mass energy of 1.96 TeV and find no evidence for a single top quark signal. The resulting 95% confidence level upper limits on the single top quark production cross sections are 6.4 pb in the s-channel and 5.0 ph in the t-channel. (c) 2005 Elsevier B.V. All rights reserved.
Search for pair production of heavy top-like quarks decaying to a high-pT W boson and a b quark in the lepton plus jets final state at s=7 TeV with t…
2013
A search is presented for production of a heavy up-type quark (t') together with its antiparticle, assuming a significant branching ratio for subsequent decay into a W boson and a b quark. The search is based on 4.7 fb(-1) of pp collisions root s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton + jets final state, characterized by a high-transverse-momentum isolated electron or muon, large missing transverse momentum and at least three jets. The analysis strategy relies on the substantial boost of the W bosons in the t'(t') over bar signal when m(t') greater than or similar to 400 GeV. No significant excess of events above t…
Measurement of the top quark mass in the dilepton channel using mT2 at CDF
2010
We present measurements of the top quark mass using mT2, a variable related to the transverse mass in events with two missing particles. We use the template method applied to tt̅ dilepton events produced in pp̅ collisions at Fermilab’s Tevatron Collider and collected by the CDF detector. From a data sample corresponding to an integrated luminosity of 3.4 fb-1, we select 236 tt̅ candidate events. Using the mT2 distribution, we measure the top quark mass to be Mtop=168.0-4.0+4.8(stat)±2.9(syst) GeV/c2. By combining mT2 with the reconstructed top quark mass distributions based on a neutrino weighting method, we measure Mtop=169.3±2.7(stat)±3.2(syst) GeV/c2. This is the first application of …
Study ofππcorrelations at LHC and RHIC energies inppcollisions within the quark-gluon string model
2011
The quark-gluon string model reproduces well the global characteristics of the $pp$ collisions at energies of $\sqrt{s}=200\text{ }\text{ }\mathrm{GeV}$ (RHIC) and $\sqrt{s}=900\text{ }\text{ }\mathrm{GeV}$ (LHC). In present paper the quark-gluon string model is employed for the description of femtoscopic characteristics of identical pions produced in the aforementioned reactions. The study is concentrated on the low multiplicity and multiplicity averaged events, where no collective effects are expected. The different procedures for fitting the one-dimensional correlation functions of pions are studied and compared with the space-time distributions extracted directly from the model. Particu…
Search for Single Vectorlike Quarks inpp¯Collisions ats=1.96 TeV
2011
We present a search for hypothetical vector-like quarks in ppbar collisions at sqrt(s) = 1.96 TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb^(-1). We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vector-like quarks decaying to W+jet and Z+jet. These are the most stringent mass limits for electroweak single vector-like quark production at hadron colliders.
Exclusive ω meson production at COMPASS
2016
Exclusive ω meson production is studied by the COMPASS Collaboration using the CERN 160 GeV/ c muon beam and a transversely polarised proton target. Single-spin and double-spin asymmetries are measured, some of which are sensitive to the Generalised Parton Distributions E that are related to quark orbital angular momenta. The results, which are sensitive also to the pion-pole contribution to the production mechanism, are compared to the predictions of a phenomenological model.
Studies of Λcproduction in pp and p-Pb collisions 1 with ALICE at 2 the LHC
2017
A Large Ion Collider Experiment (ALICE) was designed to study the strongly interacting medium created in heavy-ion collisions at LHC energies, the Quark Gluon Plasma (QGP). Heavy quarks (charm and beauty), produced in the early stages of the collisions, are among the most powerful probes to study this state of matter. To study the QGP effects, it is important to establish reference data, which is done by analysing results from pp and p-Pb collisions.We report on the charmed baryon Λc measurement in pp collisions at √s = 7 TeV and in p-Pb collisions at √sNN = 5.02 TeV with the ALICE experiment, through the reconstruction of the decay channels Λc + → p K S 0 and Λc + → pK − π + .
The EPPS16 nuclear PDFs
2017
We report on EPPS16 - the first analysis of NLO nuclear PDFs where LHC p-Pb data (Z, W, dijets) have been directly used as a constraint. In comparison to our previous fit EPS09, also data from neutrino-nucleus deeply-inelastic scattering and pion-nucleus Drell-Yan process are now included. Much of the theory framework has also been updated from EPS09, including a consistent treatment of heavy quarks in deeply-inelastic scattering. However, the most notable change is that we no longer assume flavour-blind nuclear modifications for valence and sea quarks. This significantly reduces the theoretical bias. All the analysed data are well reproduced and the analysis thereby supports the validity o…
Colloquium: New physics search with flavor in the LHC era
2013
We give a status report on quark flavour physics in view of the latest data from the B factories and the LHC, and discuss the impact of the latest experimental results on new physics in the MFV framework. We also show some examples of the implications in supersymmetry. A status report on quark flavor physics in view of the latest data from the B factories and the LHC is given, and the impact of the latest experimental results on new physics in the minimal flavor violation framework is discussed. Also shown are some examples of the implications in supersymmetry. We give a status report on quark flavour physics in view of the latest data from the B factories and the LHC, and discuss the impac…
Direct Bounds on Heavy Top-Like Quarks With Standard and Exotic Decays
2017
Heavy vector-like quarks with electric charge $Q=2/3$ (also called \textit{heavy tops}) appear naturally in many extensions of the Standard Model. Although these typically predict the existence of further particles below the TeV scale, direct searches for heavy tops have been performed assuming that they decay only into SM particles. The aim of this paper is to overcome this situation. We consider the most constraining experimental LHC searches for vector-like quarks, including analyses of the 36 fb$^{-1}$ of data collected in the latest run at 13 TeV of center of mass energy, as well as searches sensitive to heavy tops decaying into a new scalar, $S$. Combining all these, we derive bounds …