Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session J16: Top Quark / Hadronic Physics |
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Sponsoring Units: DPF Chair: Andreas Kronfeld, Fermilab Room: 251D |
Sunday, April 17, 2016 10:45AM - 10:57AM |
J16.00001: Measurement of the production cross section of a top quark pair in association with a photon in pp collisions at the LHC Titas Roy, Daniel Noonan, Francisco Yumiceva, Andrew Ivanov, Yurii Maravin, Mikhail Makouski In this analysis the production cross section of a top quark pair plus a radiated photon is measured during proton-proton collisions at the centre of mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb at the Large Hadron Collider, at CERN. The data was recorded by the Compact Muon Solenoid experiment. The signal region is defined by top quark pairs, with a radiated photon, decaying in the process pp->W+W-bb $\gamma$. The signal region is defined by photons emitted directly from top quarks as well as from its decay products. An important part of the analysis is calculation of photon purity and photon identification efficiency, which are done using data-driven methods. The cross section $\sigma_{tt\gamma}$ is measured in relation to the inclusive $\sigma_{tt}$ cross section. The measured cross section ratio agrees with the standard model expectation. [Preview Abstract] |
Sunday, April 17, 2016 10:57AM - 11:09AM |
J16.00002: ABSTRACT WITHDRAWN |
Sunday, April 17, 2016 11:09AM - 11:21AM |
J16.00003: Probing charmonium production through jet substructure at ATLAS David Bjergaard, Ayana Arce There are many open questions regarding charmonium production at hadron colliders. The color octet production mechanism of non-relativistic QCD (NRQCD) was introduced in order to describe the $p_T$ spectrum of prompt $J/\psi$ particles. This mechanism is expected to be characterized by enhanced hadronic activity around the $J/\psi$. Recently it has been suggested that jet substructure techniques may be able to discriminate between the octet and singlet production mechanisms. An ATLAS measurement of N-subjettiness and the $J/\psi$-jet momentum fraction in 8 TeV LHC proton-proton collisions will be described. [Preview Abstract] |
Sunday, April 17, 2016 11:21AM - 11:33AM |
J16.00004: Quarkonium Production at CMS Maksat Haytmyradov Quarkonium production has long been considered as an ideal means of investigating QCD and other new phenomena. The first simultaneous production of two J /$\psi$-mesons was observed in 1982 by NA3 collaboration, and later it was followed by the LHCb and CMS collaboration. At NA3, the main contribution to the cross section arises from the quark-antiquark annihilation channel. On the contrary, gluon-gluon scattering is dominant at the Tevatron and the LHC colliders. We present the studies of double quarkonium production in 20.7 fb$^{-1}$ integrated luminosity in proton-proton collisions at s $\sqrt s=$ 8 TeV. Both quarkonia are fully reconstructed from $\mu ^+$ $\mu ^-$ pairs, and preliminary cross-section of production will be reported. [Preview Abstract] |
Sunday, April 17, 2016 11:33AM - 11:45AM |
J16.00005: Simultaneously Produced Upsilon and Jpsi Production Cross Section Kamuran Dilsiz The observation and cross section of simultaneously produced $\Upsilon$ and $J/\psi$ mesons are performed using 20 $fb^{-1}$ integrated luminosity in proton-proton collisions at 8 TeV energy recorded with the CMS detector. Both mesons are fully reconstructed from their final states. To extract the signal yield, an extended maximum likelihood fit is used on two (invariant mass of $\Upsilon$ and $J/\psi$) and three (invariant mass of $\Upsilon$ and $J/\psi$, and c$\tau$) event variables. A data-based method is used to study muon reconstruction, trigger and offline selection efficiencies. The cross section in the fiducial region, defined as $p_{T}^{\mu}>3.5$ GeV/c and $|\eta^{\mu}|<2.4$ for $\Upsilon$ meson and as $p_{T}^{\mu}>2$ GeV/c and $|\eta^{\mu}|<2.4$ for $J/\psi$ meson, will be reported. [Preview Abstract] |
Sunday, April 17, 2016 11:45AM - 11:57AM |
J16.00006: Latest results on tetra- and penta-quark candidates from LHCb Thomas Britton Thanks to its unique capabilities the LHCb experiment has been making important contributions to the spectroscopy of exotic hadrons; among them the X(3872), Z(4430)$^{\mathrm{+}}$ tetraquark and the P$_{\mathrm{c}}$(4380)$^{\mathrm{+}}$, P$_{\mathrm{c}}$(4450)$^{\mathrm{+}}$ pentaquark candidates. The latest results on tetraquark and pentaquark candidates will be presented. [Preview Abstract] |
Sunday, April 17, 2016 11:57AM - 12:09PM |
J16.00007: Searching for $X(3872)$ using lattice QCD Song-haeng Lee, Carleton DeTar For decades, many excited charmonium states have been discovered that cannot be explained within the conventional quark model. Among the those mesons, the narrow charmonium-like state $X(3872)$ has been examined using various phenomenological models, however, the question for its constituent still remains open. One of the strong candidates is a $D\bar D^*$ molecular state because its mass is within $1~$MeV of the $D\bar D^*$ threshold, however, such a molecular state can’t be directly studied by perturbative QCD in such a low energy regime where the interaction of the colored quarks and gluons is very strong. Numerical simulation with lattice QCD provides a nonperturbative, ab initio method for studying this mysterious meson state. In this talk, I present preliminary simulation results for this charmonium-like states with quantum numbers $J^{\rm PC} = 1^{++}$ in both the isospin $0$ and $1$ channels. We use interpolating operators including both the conventional excited P-wave charmonium state ($\chi_{c1}$) and the $D\bar D^*$ open charm state for the isospin $0$ channel, but only $D\bar D^*$ for the isospin $1$ channel. We extract large negative S-wave scattering length and find an $X(3872)$ candidate $13\pm6$~MeV below the $D\bar D^*$ threshold in the isospin $0$ channel. [Preview Abstract] |
Sunday, April 17, 2016 12:09PM - 12:21PM |
J16.00008: Quarks, Gluons and Color are sufficient, but are they necessary? David Bartlett John Stewart Bell died in 1990. Two experiments in the last year have made one appreciate Bell's support for instantaneous action at a distance (``quantum spookiness'') and his disdain for ``hidden variables''. R. Hanson et al constructed an entangled state with electrons in two labs 1.3 km apart. At NIST, C.W. Clark et al gave a free neutron orbital angular momentum.~~The neutron joins the electron and photon as particles that can be given L. Who knows how the up and down quarks enjoyed this experience. Quarks are the most obvious hidden variable in physics. No person has isolated even one. Consequently, the standard model features ``Quark Confinement'' [K.G. Wilson, 1974]. Unfortunately confinement complicates the comparison of QED and QCD. [ K. G. Wilson, T.S. Walhout, A. Harindranath,W-M Zhang, R. J. Perry, and S.Z. Glazek (1994)]. The alternatives to quarks are scattering lengths, resonances, octets, decuplets, and singlets. This talk will elucidate some of the pre LHC tensions in the standard model. Why is strangeonium qualitatively different from charmonium~~and bottomonium . Why does the process $\gamma \quad + \quad \gamma \quad \to $~~$\eta \quad + \quad \eta $ (Belle 2010) have a resonance at just the mass of the J/psi, but with a forward {\&} backward peaked angular distribution that contrasts with the isotropy of the J/psi(1S)(1974)? What is needed to show that it is really the off-diagonal elements in the K-mass matrix that are responsible for CP violation (CPLEAR 1999). [Preview Abstract] |
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