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ALICE Collaboration,Abelev, B.,Adam, J.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad, N.,Ahmad Masoodi, A.,Ahn, S.A.,Ahn North-Holland Pub. Co 2012 Physics letters: B Vol.718 No.2
The p<SUB>T</SUB>-differential inclusive production cross section of the prompt charm-strange meson D<SUB>s</SUB><SUP>+</SUP> in the rapidity range |y|<0.5 was measured in proton-proton collisions at s=7 TeV at the LHC using the ALICE detector. The analysis was performed on a data sample of 2.98x10<SUP>8</SUP> events collected with a minimum-bias trigger. The corresponding integrated luminosity is L<SUB>int</SUB>=4.8 nb<SUP>-1</SUP>. Reconstructing the decay D<SUB>s</SUB><SUP>+</SUP>→φπ<SUP>+</SUP>, with φ→K<SUP>-</SUP>K<SUP>+</SUP>, and its charge conjugate, about 480 D<SUB>s</SUB><SUP>+/-</SUP> mesons were counted, after selection cuts, in the transverse momentum range 2<p<SUB>T</SUB><12 GeV/c. The results are compared with predictions from models based on perturbative QCD. The ratios of the cross sections of four D meson species (namely D<SUP>0</SUP>, D<SUP>+</SUP>, D<SUP>@?+</SUP> and D<SUB>s</SUB><SUP>+</SUP>) were determined both as a function of p<SUB>T</SUB> and integrated over p<SUB>T</SUB> after extrapolating to full p<SUB>T</SUB> range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in e<SUP>+</SUP>e<SUP>-</SUP>, ep and pp interactions at various centre-of-mass energies.
Measurement of an Excess in the Yield ofJ/ψat Very LowpTin Pb-Pb Collisions atsNN=2.76 TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Aleksandrov, D.,Alessandro, B.,Alexandre, D.,Alfaro M American Physical Society 2016 Physical review letters Vol.116 No.22
<P>We report on the first measurement of an excess in the yield of J/psi at very low transverse momentum (pT < 0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at root s(NN) = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/psi in the rapidity range 2.5 < y < 4 reaches about 7 (2) in the p(T) range 0-0.3 GeV/c in the 70%-90% (50%-70%) centrality class. The J/psi production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/psi is the underlying physics mechanism. If confirmed, the observation of J/psi coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the quark-gluon plasma.</P>
Correlated Event-by-Event Fluctuations of Flow Harmonics in Pb-Pb Collisions at sNN=2.76 TeV
Adam, J.,Adamová,, D.,Aggarwal, M. M.,Aglieri Rinella, G.,Agnello, M.,Agrawal, N.,Ahammed, Z.,Ahmad, S.,Ahn, S. U.,Aiola, S.,Akindinov, A.,Alam, S. N.,Albuquerque, D. S. D.,Aleksandrov, D.,Aless American Physical Society 2016 Physical Review Letters Vol.117 No.18
<P>We report the measurements of correlations between event-by-event fluctuations of amplitudes of anisotropic flow harmonics in nucleus-nucleus collisions, obtained for the first time using a new analysis method based on multiparticle cumulants in mixed harmonics. This novel method is robust against systematic biases originating from nonflow effects and by construction any dependence on symmetry planes is eliminated. We demonstrate that correlations of flow harmonics exhibit a better sensitivity to medium properties than the individual flow harmonics. The new measurements are performed in Pb-Pb collisions at the center-of-mass energy per nucleon pair of root S-NN = 2.76 TeV by the ALICE experiment at the Large Hadron Collider. The centrality dependence of correlation between event-by-event fluctuations of the elliptic v(2) and quadrangular v(4) flow harmonics, as well as of anticorrelation between v(2) and triangular v(3) flow harmonics are presented. The results cover two different regimes of the initial state configurations: geometry dominated (in midcentral collisions) and fluctuation dominated (in the most central collisions). Comparisons are made to predictions from Monte Carlo Glauber, viscous hydrodynamics, AMPT, and HIJING models. Together with the existing measurements of the individual flow harmonics the presented results provide further constraints on the initial conditions and the transport properties of the system produced in heavy-ion collisions.</P>
J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV
ALICE Collaboration,Abelev, B.,Adam, J.,Adamova, D.,Adare, A.M.,Aggarwal, M.M.,Aglieri Rinella, G.,Agocs, A.G.,Agostinelli, A.,Aguilar Salazar, S.,Ahammed, Z.,Ahmad Masoodi, A.,Ahmad, N.,Ahn, S.U.,Aki North-Holland Pub. Co 2012 Physics letters: B Vol.712 No.3
The ALICE Collaboration reports the measurement of the relative J/ψ yield as a function of charged particle pseudorapidity density dN<SUB>ch</SUB>/dη in pp collisions at s=7 TeV at the LHC. J/ψ particles are detected for p<SUB>t</SUB>>0, in the rapidity interval |y|<0.9 via decay into e<SUP>+</SUP>e<SUP>-</SUP>, and in the interval 2.5<y<4.0 via decay into μ<SUP>+</SUP>μ<SUP>-</SUP> pairs. An approximately linear increase of the J/ψ yields normalized to their event average (dN<SUB>J/ψ</SUB>/dy)/<dN<SUB>J/ψ</SUB>/dy> with (dN<SUB>ch</SUB>/dη)/<dN<SUB>ch</SUB>/dη> is observed in both rapidity ranges, where dN<SUB>ch</SUB>/dη is measured within |η|<1 and p<SUB>t</SUB>>0. In the highest multiplicity interval with <dN<SUB>ch</SUB>/dη(bin)≥24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/ψ yield by a factor of about 5 at 2.5<y<4 (8 at |y|<0.9) is observed.
CMS Collaboration,Chatrchyan, S.,Khachatryan, V.,Sirunyan, A.M.,Tumasyan, A.,Adam, W.,Bergauer, T.,Dragicevic, M.,Ero, J.,Fabjan, C.,Friedl, M.,Fruhwirth, R.,Ghete, V.M.,Hammer, J.,Hormann, N.,Hrubec, North-Holland Pub. Co 2012 Physics letters: B Vol.714 No.2
The Λ<SUB>b</SUB> differential production cross section and the cross section ratio σ(Λ@?<SUB>b</SUB>)/σ(Λ<SUB>b</SUB>) are measured as functions of transverse momentum p<SUB>T</SUB><SUP>Λ'b</SUP> and rapidity |y<SUP>Λ'b</SUP>| in pp collisions at s=7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Λ<SUB>b</SUB> decays reconstructed in the exclusive final state J/ψΛ, with the subsequent decays J/ψ→μ<SUP>+</SUP>μ<SUP>-</SUP> and Λ→pπ, using a data sample corresponding to an integrated luminosity of 1.9 fb<SUP>-1</SUP>. The product σ(Λ<SUB>b</SUB>)xB(Λ<SUB>b</SUB>→J/ψΛ) versus p<SUB>T</SUB><SUP>Λ'b</SUP> falls faster than that of b mesons. The measured value of σ(Λ<SUB>b</SUB>)xB(Λ<SUB>b</SUB>→J/ψΛ) for p<SUB>T</SUB><SUP>Λ'b</SUP>>10 GeV and |y<SUP>Λ'b</SUP>|<2.0 is 1.16+/-0.06+/-0.12 nb, and the integrated σ(Λ@?<SUB>b</SUB>)/σ(Λ<SUB>b</SUB>) ratio is 1.02+/-0.07+/-0.09, where the uncertainties are statistical and systematic, respectively.
Bs0lifetime measurement in theCP-odd decay channelBs0→J/ψ f0(980)
Abazov, V. M.,Abbott, B.,Acharya, B. S.,Adams, M.,Adams, T.,Agnew, J. P.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Askew, A.,Atkins, S.,Augsten, K.,Aushev, V.,Aushev, Y.,Avila, C.,Badaud, F.,Bagby, L.,Bal American Physical Society 2016 Physical Review D Vol.94 No.1
<P>The lifetime of the B-s(0) meson is measured in the decay channel B-s(0) -> J/Psi pi(+)pi(-) with 880 <= M pi+pi- <= 1080 MeV/c(2), which is mainly a CP-odd state and dominated by the f(0)(980) resonance. In 10.4 fb(-1) of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the B-s(0) meson is measured to be tau(B-s(0)) = 1.70 +/- 0.14(stat) +/- 0.05(syst) ps. Neglecting CP violation in B-s(0)/(B) over bar (0)(s) mixing, the measurement can be translated into the width of the heavy mass eigenstate of the B-s(0), Gamma(H) = 0.59 +/- 0.05(stat) +/- 0.02(syst) ps(-1).</P>
Study of the X±(5568) state with semileptonic decays of the Bs0 meson
Abazov, V. M.,Abbott, B.,Acharya, B. S.,Adams, M.,Adams, T.,Agnew, J. P.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Askew, A.,Atkins, S.,Augsten, K.,Aushev, V.,Aushev, Y.,Avila, C.,Badaud, F.,Bagby, L.,Bal American Physical Society 2018 Physical Review D Vol.97 No.9
<P>We present a study of the X-+/-(5568) using semileptonic decays of the B-s(0) meson using the full run II integrated luminosity of 10.4 fb(-1) in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the DO detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, X-+/-(5568), in the decay sequence X-+/-(5568) -> B-s(0) pi(+/-) where B-s(0)-> mu(-/+) (DsX)-X-+/-, D-s(+/-)-> phi pi(+/-)which is consistent with the previous measurement by the DO Collaboration in the hadronic decay mode, X-+/-(5568) -> B-s(0)pi(+/-) where B-s(0 )-> J/psi phi. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding m = 5566.9(-3.1)(+3.2)(stat)(-1.2)(+0.6)(syst) MeV/c(2), Gamma = 18.6(-6.1)(+7.9)(stat)(-3.8)(+3.5) (syst) McV/c(2) with a significance of 6.7 sigma.</P>
Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data
Aartsen, M.G.,Ackermann, M.,Adams, J.,Aguilar, J.A.,Ahlers, M.,Ahrens, M.,Altmann, D.,Anderson, T.,Arguelles, C.,Arlen, T.C.,Auffenberg, J.,Bai, X.,Barwick, S.W.,Baum, V.,Beatty, J.J.,Becker Tjus, J. North-Holland 2015 Astroparticle physics Vol.66 No.-
<P><B>Abstract</B></P> <P>Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of ∼ 60 TeV to the PeV-scale [1]. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years of IceCube data, taken between 2008 and 2011. The first method is an autocorrelation test, applied separately to the northern and southern sky. The second method is a multipole analysis, which expands the measured data in the northern hemisphere into spherical harmonics and uses the resulting expansion coefficients to separate signal from background. With both methods, the results are consistent with the background expectation with a slightly more sparse spatial distribution, corresponding to an underfluctuation. Depending on the assumed number of sources, the resulting upper limit on the flux per source in the northern hemisphere for an <SUP> E - 2 </SUP> energy spectrum ranges from ∼ 1.5 · <SUP> 10 - 8 </SUP> GeV/cm<SUP>2</SUP> s<SUP>−1</SUP>, in the case of one assumed source, to ∼ 4 · <SUP> 10 - 10 </SUP> GeV/cm<SUP>2</SUP> s<SUP>−1</SUP>, in the case of 3500 assumed sources.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We applied two methods to search for clusters of astrophysical neutrinos on background. </LI> <LI> Investigated both hemispheres separately and three different energy spectra. </LI> <LI> Saw underfluctuation consistent with background and set limits on astrophysical flux. </LI> <LI> Compared limits to recently found astrophysical flux to constrain number of sources. </LI> <LI> Excluded few sources of very hard energy spectra for seen astrophysical flux. </LI> </UL> </P>
Search for theX(4140)state inB+→J/ψϕK+decays with the D0 detector
Abazov, V. M.,Abbott, B.,Acharya, B. S.,Adams, M.,Adams, T.,Agnew, J. P.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Askew, A.,Atkins, S.,Augsten, K.,Avila, C.,Badaud, F.,Bagby, L.,Baldin, B.,Bandurin, D. V American Physical Society 2014 PHYSICAL REVIEW D - Vol.89 No.1
<P>We investigate the decay B+ -> J/psi phi K+ in a search for the X(4140) state, a narrow threshold resonance in the J/psi phi system. The data sample corresponds to an integrated luminosity of 10.4 fb(-1) of p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. We observe a mass peak with a statistical significance of 3.1 standard deviations and measure its invariant mass to be M = 4159.0 +/- 4.3(stat) +/- 6.6(syst) MeV and its width to be Gamma = 19.9 +/- 12.6(stat)(-8.0)(+3.0)(syst) MeV.</P>
Aaltonen, T.,Abazov, V. M.,Abbott, B.,Acharya, B. S.,Adams, M.,Adams, T.,Agnew, J. P.,Alexeev, G. D.,Alkhazov, G.,Alton, A.,Amerio, S.,Amidei, D.,Anastassov, A.,Annovi, A.,Antos, J.,Apollinari, G.,App American Physical Society 2015 Physical Review Letters Vol.115 No.15
<P>We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb(-1) per experiment. The t-channel cross section is measured to be sigma(t) = 2.25(-0.31)(+0.29) pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s + t channel cross section measurement resulting in sigma(s+t) = 3.30(-0.40)(+0.52) pb, without assuming the standard model value for the ratio sigma(s)/sigma(t). The resulting value of the magnitude of the top-to-bottom quark coupling is vertical bar V-tb vertical bar = 1.02(-0.05)(+0.06), corresponding to vertical bar V-tb vertical bar > 0.92 at the 95% C. L.</P>