787 research outputs found
f(1285) Formation in Two-Photon Collisions at LEP
No full textThe final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209~GeV with an integrated luminosity of 664.6~pb. The f(1285) meson is observed and the dependence of its production is compared to different form factor models. The -coupling parameter is found to be ~keV. The branching fraction is also measured.The ηπ + π − final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb −1 . The f 1 (1285) meson is observed and the Q 2 dependence of its production is compared to different form factor models. The γγ -coupling parameter Γ γγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ (f 1 (1285)→a 0 π )/ Γ (f 1 (1285)→ ηππ ) is also measured.The eta pi^+ pi^- final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6/pb. The f_1(1285) meson is observed and the Q^2 dependence of its production is compared to different form factor models. The gamma-gamma coupling parameter is found to be 3.5 +/- 0.6(stat.) +/- 0.5(sys.) keV. The branching fraction (f_1(1285) -> a_0 pi) / (f_1(1285) -> eta pi pi) is also measured
Search for Next-to-Minimal Supersymmetric Higgs Bosons in the h -> aa ->mu mu mu mu, mu mu tau tau Channels Using pp Collisions at s=1.96 TeV
No full textContains fulltext :
75918.pdf (author's version ) (Open Access
The Q(2) evolution of the hadronic photon structure function F-2(gamma) at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008
No full textNew measurements at a centre-of-mass energy root s similar or equal to 183 GeV of the hadronic photon structure function F-2(gamma)(x) in the Q(2) interval, 9 GeV2 less than or equal to Q(2) less than or equal to 30 GeV2, are presented. The data, collected in 1997 with the L3 detector, correspond to an integrated luminosity of 51.9 pb(-1). Combining with the data taken at a centre-of-mass energy of 91 GeV, the evolution of F-2(gamma) With Q(2) is measured in the Q(2) range from 1.2 GeV2 to 30 GeV2. F-2(gamma) shows a linear growth with ln Q(2); the value of the slope alpha(-1)d F-2(gamma)(Q(2))/dlnQ(2) is measured in two x bins from 0.01 to 0.2 and is somewhat higher than predicted. (C) 1999 Published by Elsevier Science B.V. All rights reserved
Study of the hadronic photon structure function at LEP
No full textThe hadronic photon structure function is studied in the reaction at LEP with the L3 detector. The data, collected from 1991 to 1995 at a centre-of-mass energy \sqrt{s} \simeq 91 \GeV, correspond to an integrated luminosity of 140~pb. The photon structure function is measured in the interval 1.2 \GeV^2 \leq Q^2 \leq 9.0 \GeV^2 and the interval . \FF shows a linear growth with . The value of the slope \alpha^{-1}\mathrm{d}\FF(Q^2)/\mathrm{d}\ln{Q^2} is measured to be
Measurement of the photon structure function F-2(gamma) with the L3 detector at LEP
No full textThe e(+)e(-) -\u3e e(+)e(-)hadrons reaction, where one of the two electrons is detected in a low polar-angle calorimeter, is analysed in order to measure the hadronic photon structure function F-2(gamma) The full high-energy and high-luminosity data set, collected with the U detector at centre-of-mass energies 189 GeV \u3c= root s \u3c= 209 GeV, corresponding to an integrated luminosity of 608 pbis used. The Q(2) range 11 GeV2 \u3c= Q(2) \u3c= 34 GeV2 and the x range 0.006 \u3c= x \u3c= 0.556 are considered. The data are compared with recent parton density functions. (c) 2005 Published by Elsevier B.V
Jet suppression and jet substructure in Pb+Pb and Xe+Xe collisions with the ATLAS detector
No full textThis short summary presents latest measurements of the nuclear modification factor, , for jets in Pb+Pb collisions at = 5.02 TeV with the ATLAS detector at the LHC. The analysis is performed over a large range of transverse momentum, up to TeV, and differentially in jet , rapidity, and collision centrality. The jet is measured also differentially in the jet mass which provides a new information on the dependence of the energy loss on the substructure of jets. Latest results on the dijet momentum balance in Xe+Xe collisions at = 5.44 TeV are presented and compared to the same quantity measured in Pb+Pb collisions = 5.02 TeV. These recent measurements should help us understand mechanisms of parton energy loss and properties of hot and dense matter created in heavy-ion collisions
Search for Higgs boson decays into two new low-mass spin-0 particles in the 4 channel with the ATLAS detector using collisions at TeV
No full textThis paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into -quark pairs, , using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy TeV. This search focuses on the regime where the decay products are collimated and in the range GeV and is complementary to a previous search in the same final state targeting the regime where the decay products are well separated and in the range GeV. A novel strategy for the identification of the decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross-section of , where the Higgs boson is produced in association with a boson.This paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into -quark pairs, , using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy TeV. This search focuses on the regime where the decay products are collimated and in the range GeV and is complementary to a previous search in the same final state targeting the regime where the decay products are well separated and in the range GeV. A novel strategy for the identification of the decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross-section of , where the Higgs boson is produced in association with a boson.This paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into -quark pairs, , using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy TeV. This search focuses on the regime where the decay products are collimated and in the range GeV and is complementary to a previous search in the same final state targeting the regime where the decay products are well separated and in the range GeV. A novel strategy for the identification of the decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross-section of , where the Higgs boson is produced in association with a boson
Search for Higgs boson decays into two new low-mass spin-0 particles in the 4b channel with the ATLAS detector using pp collisions at s =13 TeV
No full textThis paper describes a search for beyond the Standard Model decays of the Higgs boson into a pair of new spin-0 particles subsequently decaying into b-quark pairs, H→aa→(bb ̄)(bb ̄), using proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider at center-of-mass energy s=13 TeV. This search focuses on the range 15 GeV≤ma≤30 GeV, where the decay products are collimated; it is complementary to a previous search in the same final state targeting the range 20 GeV≤ma≤60 GeV, where the decay products are well separated. A novel strategy for the identification of the a→bb ̄ decays is deployed to enhance the efficiency for topologies with small separation angles. The search is performed with 36 fb-1 of integrated luminosity collected in 2015 and 2016 and sets upper limits on the production cross section of H→aa→(bb ̄)(bb ̄), where the Higgs boson is produced in association with a Z boson
Neutral-current four-fermion production in e(+)e(-) interactions at LEP
No full textNeutral-current four-fermion production, e(+)e(-) f (f) over bar f\u27(f) over barf, is studied in 0.7 fb(-1) of data collected with the L3 detector at LEP at centre-of-mass energies root s = 183-209 GeV. Four final states are considered: q (q) over barv (v) over bar, q (q) over barl(+)l(-),l(+)l(-)l\u27(+)l\u27(-) and l(+)l(-)v (v) over bar, where l denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e(+)e(-) -\u3e Z gamma* -\u3e f (f) over barf\u27(f) over bar\u27 process is studied and its total cross section at the average centre-of-mass energy (root s) = 196.6 GeV is found to be 0.29 +/- 0.05 +/- 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the q (q) over barl(+)l(-) final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found. (c) 2005 Published by Elsevier B.V
Charged-hadron production in pp, p plus Pb, Pb plus Pb, and Xe plus Xe collisions at √sNN=5 TeV with the ATLAS detector at the LHC
No full textThis paper presents measurements of charged-hadron spectra obtained in pp, p+Pb, and Pb+Pb collisions at s or sNN = 5.02 TeV, and in Xe+Xe collisions at sNN = 5.44 TeV. The data recorded by the ATLAS detector at the LHC have total integrated luminosities of 25 pb −1, 28 nb −1, 0.50 nb −1, and 3 μb −1, respectively. The nuclear modification factors RpPb and R AA are obtained by comparing the spectra in heavy-ion and pp collisions in a wide range of charged-particle transverse momenta and pseudorapidity. The nuclear modification factor RpPb shows a moderate enhancement above unity with a maximum at p T ≈ 3 GeV; the enhancement is stronger in the Pb-going direction. The nuclear modification factors in both Pb+Pb and Xe+Xe collisions feature a significant, centrality-dependent suppression. They show a similar distinct p T-dependence with a local maximum at p T ≈ 2 GeV and a local minimum at p T ≈ 7 GeV. This dependence is more distinguishable in more central collisions. No significant |η|-dependence is found. A comprehensive comparison with several theoretical predictions is also provided. They typically describe R AA better in central collisions and in the p T range from about 10 to 100 GeV. [Figure not available: see fulltext.
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