Search results for "Collider"
showing 10 items of 1690 documents
Measurement of theϕη*distribution of muon pairs with masses between 30 and 500 GeV in10.4 fb−1ofpp¯collisions
2015
We present a measurement of the distribution of the variable phi(eta)* for muon pairs with masses between 30 and 500 GeV, using the complete run II data set collected by the D0 detector at the Fermilab Tevatron proton-antiproton collider. This corresponds to an integrated luminosity of 10.4 fb(-1) at root s = 1.96 TeV. The data are corrected for detector effects and presented in bins of dimuon rapidity and mass. The variable phi(eta)* probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. These are the first measurements at any collider of the phi(eta)* distributions for dilepton masses aw…
Search for displaced muonic lepton jets from light Higgs boson decay in proton–proton collisions at s=7 TeV with the ATLAS detector
2013
A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at root s = 7 TeV centre-of-mass ...
Search for pair production of first or second generation leptoquarks in proton-proton collisions ats=7 TeVusing the ATLAS detector at the LHC
2011
This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb(-1) of proton-proton collision data recorded by the ATLAS detector at root s = 7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M-LQ < 376 (319) GeV and M-LQ < 422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of …
Search for long-lived, heavy particles in final states with a muon and multi-track displaced vertex in proton–proton collisions at s=7 TeV with the A…
2013
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. In this Letter, results are presented of a search for events containing one or more such particles, which decay at a significant distance from their production point, using a final state containing charged hadrons and an associated muon. This analysis uses a data sample of proton-proton collisions at root s = 7 TeV corresponding to an integrated luminosity of 4.4 fb(-1) collected in 2011 by the ATLAS detector operating at the Large Hadron Collider. Results are interpreted in the context of R-parity violating supersymmetric scenarios. No events in the signal region are observed and limits are se…
Collider probes of axion-like particles.
2017
Axion-like particles (ALPs), which are gauge-singlets under the Standard Model (SM), appear in many well-motivated extensions of the SM. Describing the interactions of ALPs with SM fields by means of an effective Lagrangian, we discuss ALP decays into SM particles at one-loop order, including for the first time a calculation of the $a\to\pi\pi\pi$ decay rates for ALP masses below a few GeV. We argue that, if the ALP couples to at least some SM particles with couplings of order $(0.01-1) \mbox{TeV}^{-1}$, its mass must be above 1 MeV. Taking into account the possibility of a macroscopic ALP decay length, we show that large regions of so far unconstrained parameter space can be explored by se…
Search for type-III seesaw heavy leptons inppcollisions ats=8 TeVwith the ATLAS detector
2015
A search for the pair production of heavy leptons (N-0, L-+/-) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N-0 -> W(+/-)l(+/-) (l = e, mu, tau) and L-+/- -> W(+/-)v (v = v(e), v(mu), v(tau)) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. H…
A study of ccc¯c¯ tetraquark decays in 4 muons and in D(⁎)D¯(⁎) at LHC
2020
Abstract We perform a quantitative analysis of the decays of c c c ¯ c ¯ tetraquarks with J P C = 0 + + , 2 + + into 4 muons and into hidden- and open-charm mesons and estimate, for the first time, the fully charmed tetraquark decay width. The calculated cross section upper limit is ∼ 39 ( 780 ) fb for the 4 muons channel, and ∼ 42 ( 616 ) pb for the D ( ⁎ ) D ¯ ( ⁎ ) → e μ channel, in the 0 + + ( 2 + + ) case. Decay widths depend upon the additional parameter ξ = | Ψ T ( 0 ) | 2 / | Ψ J / ψ ( 0 ) | 2 , which can be computed with a considerable error. We find Γ ( 0 + + ) ∼ Γ ( 2 + + ) = 97 ± 30 . On the basis of our results and with the present sensitivity, LHCb should detect both 0 + + and…
Performance of the ATLAS liquid argon endcap calorimeter in the pseudorapidity region in beam tests
2008
Abstract The pseudorapidity region 2.5 | η | 4.0 in ATLAS is a particularly complex transition zone between the endcap and forward calorimeters. A set-up consisting of 1 4 resp. 1 8 of the full azimuthal acceptance of the ATLAS liquid argon endcap and forward calorimeters has been exposed to beams of electrons, pions and muons in the energy range E ⩽ 200 GeV at the CERN SPS. Data have been taken in the endcap and forward calorimeter regions as well as in the transition region. This beam test set-up corresponds very closely to the geometry and support structures in ATLAS. A detailed study of the performance in the endcap and forward calorimeter regions is described. The data are compared wit…
Production of muons from heavy-flavour hadron decays in p–Pb collisions at sNN=5.02 TeV
2017
Abstract The production of muons from heavy-flavour hadron decays in p–Pb collisions at s NN = 5.02 TeV was studied for 2 p T 16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 y cms 3.53 and − 4.46 y cms − 2.96 , respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum ( p T ). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 p T 3.5 GeV/c, it is above unity by more than 2σ. Th…
Search for a Higgs boson produced in association with a Z boson
2007
We describe a search for the Standard Model Higgs boson with a mass of 105 GeV/c(2) to 145 GeV/c(2) in data corresponding to an integrated luminosity of approximately 450 pb(-1) collected with the D phi detector at the Fermilab Tevatron p (p) over bar collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a b (b) over bar pair. The data are well described by the expected background, leading to 95% confidence level cross section upper limits sigma (p (p) over bar -> ZH) x B(H -> b (b) over bar) in the range of 3.1 pb to 4.4 pb.