Search results for "hadron"
showing 10 items of 3505 documents
Search for New Bottomlike Quark Pair DecaysQQ¯→(tW∓)(t¯W±)in Same-Charge Dilepton Events
2010
We report the most restrictive direct limits on masses of fourth-generation down-type quarks b{sup '}, and quarklike composite fermions (B or T{sub 5/3}), decaying promptly to tW{sup +}-. We search for a significant excess of events with two same-charge leptons (e, mu), several hadronic jets, and missing transverse energy. An analysis of data from pp collisions with an integrated luminosity of 2.7 fb{sup -1} collected with the CDF II detector at Fermilab yields no evidence for such a signal, setting mass limits m{sub b}{sup '}, m{sub B}>338 GeV/c{sup 2} and m{sub T{sub 5{sub /{sub 3}}}}>365 GeV/c{sup 2} at 95% confidence level.
Search for the Production of Scalar Bottom Quarks inpp¯Collisions ats=1.96 TeV
2010
We report on a search for direct scalar bottom quark (sbottom) pair production in pp collisions at {radical}(s)=1.96 TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a b quark. The study uses a collider detector at Fermilab Run II data sample corresponding to 2.65 fb{sup -1} of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits on the sbottom pair production cross se…
Lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs)
2016
An ongoing program of evaluating TMD observables within Lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Data on the naively T-odd Sivers and Boer-Mulders effects as well as the transversity TMD are presented.
EPPS16 – First nuclear PDFs to include LHC data
2017
We present results of our recent EPPS16 global analysis of NLO nuclear parton distribution functions (nPDFs). For the first time, dijet and heavy gauge boson production data from LHC proton–lead collisions have been included in a global fit. Especially, the CMS dijets play an important role in constraining the nuclear effects in gluon distributions. With the inclusion of also neutrino–nucleus deeply-inelastic scattering and pion–nucleus Drell–Yan data and a proper treatment of isospin-corrected data, we were able to free the flavor dependence of the valence and sea quark nuclear modifications for the first time. This gives us less biased, yet larger, flavor by flavor uncertainty estimates. …
Instanton induced quark dynamics and the pentaquark
2004
We analyze the existence of the exotic $\Theta^+$ from the perspective of instanton induced quark dynamics. The 't Hooft interaction gives strong attraction in specific channels of the triquark $ud\bar s$ and diquark $ud$ configurations. In particular it leads to a light $ud\bar s$ triquark cluster, with the mass around $750 {\rm MeV}$, in the I=0, $S=1/2$ and color 3 configuration, and a light $ud$-diquark configuration, with mass $440 {\rm MeV}$, in the I=0, S=0 and color {$\bar{3}$} configuration. If we consider the pentaquark as a bound state of such triquark and diquark configurations in a relative L=1 state we obtain good agreement with the data. The small width of $\Theta^+$ has a na…
Search for New Phenomena intt¯Events with Large Missing Transverse Momentum in Proton-Proton Collisions ats=7 TeVwith the ATLAS Detector
2012
A search for new phenomena in tt events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04 fb-1 of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb …
Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at s=13 TeV with the ATLAS Detector
2018
A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T -> Zt/Wb/Ht, B -> Zb/Wt/Hb) is performed using 36.1 fb(-1) of pp ...
Search for Scalar Charm Quark Pair Production inppCollisions ats=8 TeVwith the ATLAS Detector
2015
The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal super-symmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper li…
A search for quarks in the CERN SPS neutrino beam
1978
Quarks and leptons are the only pointlike particles known so far. However, a search for a proton-breaking mechanism in high-energy neutrino-nucleon interactions had never been performed. We present here the results of the first experiment in this field.
Open-charm production measurements in pp, 1 p-Pb and Pb-Pb collisions with ALICE at the LHC
2017
ALICE (A Large Ion Collider Experiment) is designed to study the strongly in teracting matter, the Quark-Gluon Plasma (QGP), created in heavy-ion collisions at LHC energies. Charm and beauty quarks are powerful probes to study the QGP. Produced in hard partonic scattering processes on a short time scale, they are expected to traverse the QCD medium, interacting with its constituents and losing energy through radiative and collisional processes. In ALICE, open-charm production is studied through the reconstruction of the hadronic decays of D 0 , D + , D *+ and D s + mesons at mid-rapidity. High precision tracking, good vertexing capabilities and excellent particle identification offered by A…