Bulletin of the American Physical Society
2008 APS April Meeting and HEDP/HEDLA Meeting
Volume 53, Number 5
Friday–Tuesday, April 11–15, 2008; St. Louis, Missouri
Session J11: QCD and Colliders I |
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Sponsoring Units: DPF Chair: Claude Bernard, Washington University Room: Hyatt Regency St. Louis Riverfront (formerly Adam's Mark Hotel), St. Louis B |
Sunday, April 13, 2008 10:45AM - 10:57AM |
J11.00001: Direct Photon Production in Association with a Heavy Quark Tzvetalina Stavreva, Joseph F. Owens The inclusive cross section for a direct photon and a heavy quark (charm or bottom), $p+\bar p (p) \rightarrow \gamma +Q +X$, is calculated up to second order in the strong coupling constant $\alpha_s$. The photon fragmentation function, which is of order $\alpha/\alpha_s$, where $\alpha$ is the electromagnetic coupling constant, needs to be convoluted with all QCD subprocesses of order $\alpha_s^3$ containing a heavy quark in the final state so that the cross section is complete to next-to-leading order (NLO). This calculation extends previous efforts by including this NLO contribution. The cross section for photon plus heavy quark production can provide a useful check of the method used for the calculation of the heavy quark's parton distribution functions, which are currently determined with the use of the Altarelli-Parisi equation. The dependence of the cross section on the photon and heavy quark transverse momenta and rapidities will be examined. Predictions for both the Tevatron and the LHC will be presented. [Preview Abstract] |
Sunday, April 13, 2008 10:57AM - 11:09AM |
J11.00002: Search for transitions in bottomonium involving a single pseudoscalar meson Todd Pedlar Using approximately 9 million $\Upsilon(2S)$ decays and 6 million $\Upsilon(3S)$ decays, the CLEO Collaboration has searched for rare hadronic transitions between the $\Upsilon$ states involving a single $\pi^0$ or $\eta$ meson. We present the results of the measurements or upper limits for each of the following transitions: $\Upsilon(3S)\to\Upsilon(1S)(\pi^0\;\mbox{or }\eta)$, $\Upsilon(3S)\to\Upsilon(2S)\pi^0$,$\Upsilon(2S)\to\Upsilon(1S)(\pi^0\;\mbox{or }\eta)$. [Preview Abstract] |
Sunday, April 13, 2008 11:09AM - 11:21AM |
J11.00003: Hadronic jet-vertex association in a high-luminosity environment at the LHC David Miller The LHC physics program will ultimately probe not only the highest energies ever produced in the laboratory but also the most numerous and frequent collisions between hadronic particles ever. These particle luminosities, much above the current Tevatron values, will produce hadronic jets from simultaneous uncorrelated proton-proton collisions in unprecedented numbers, thus introducing challenges for jet identification and association with the primary collision vertices, jet energy measurements and missing energy resolution. We continue work first introduced by the Tevatron experiments to combine tracking information with calorimeter jets in order to disentangle this jet background. Using an algorithm which assigns a jet-vertex association probability, jet selection is shown to be insensitive to the contributions from these ``pile-up'' collisions, which is essential for the many physics analyses dependent on event jet multiplicity. Furthermore, jet-by-jet multiple interaction energy corrections are now possible and improvements to the primary vertex identification from jet-vertex association are gained for several interesting physics processes. [Preview Abstract] |
Sunday, April 13, 2008 11:21AM - 11:33AM |
J11.00004: Jet Shape Studies at CMS Pelin Kurt CMS detector will detect high transverse momentum jets produced in the final state of proton-proton collisions at the center of mass energy of 14 TeV. These data will allow to measure jet shapes, defined as the fractional transverse momentum distribution inside the jets as a function of the distance from the jet axis. Since jet shapes are sensitive to parton shower and hadronization processes, they provide a good test of perturbative QCD predictions. Calorimeter towers are used to reconstruct the differential jet shapes. We present studies performed to measure jet shapes in CMS using different clustering algorithms. [Preview Abstract] |
Sunday, April 13, 2008 11:33AM - 11:45AM |
J11.00005: ABSTRACT WITHDRAWN |
Sunday, April 13, 2008 11:45AM - 11:57AM |
J11.00006: Using Drell-Yan to Probe the Underlying Event in Run 2 at CDF Deepak Kar, Rick Field We study the event topology in Drell-Yan lepton-pair production in proton-antiproton collisions at $1.96$ TeV in Run 2 at CDF. We use the direction of the lepton-pair at a event by event basis to define three regions of $\eta-\phi $ space; ``toward'', ``away'', and ``transverse.'' The ``transverse'' region is very sensitive to the ``underlying event'' and is separated into a MAX and MIN ``transverse'' region, which helps separate the ``hard component'' (initial and final-state radiation) from the ``beam-beam remnant'' and multiple parton interaction components of the scattering. The data are corrected to the particle level and are then compared with the QCD Monte Carlo models. The properties of the ``underlying event'' are examined as a function of the lepton-pair invariant mass and transverse momentum. The data are also compared with a previous analysis on the behavior of the ``underlying event'' in high transverse momentum jet production. The goal is to improve our understanding and modeling of the high energy collider events to allow for more precise predictions at the LHC. [Preview Abstract] |
Sunday, April 13, 2008 11:57AM - 12:09PM |
J11.00007: A Numerical Approach to Coulomb Gauge QCD Hrayr Matevosyan, Adam Szczepaniak, Patrick Bowman We calculate the ghost two-point function in Coulomb gauge QCD with a simple model vacuum gluon wavefunction using Monte-Carlo integration. This approach extends the previous analytic studies of the ghost propagator in this ansatz, where a ladder-rainbow expansion was unavoidable for calculating the path integral over gluon field configurations. This approach allows us to study the possible critical behavior of the coupling constant, as well as the Coulomb potential derived from the ghost dressing function. [Preview Abstract] |
Sunday, April 13, 2008 12:09PM - 12:21PM |
J11.00008: A parametrization of the baryon octet and decuplet masses Phuoc Ha We construct a general parametrization of the baryon octet and decuplet masses including the three-body terms using the unit operator and the symmetry-breaking factors, $M^d=\textrm{diag}\,(0,1,0)$ and $M^s=\textrm{diag}\,(0,0,1)$, in conjunction with the spin operators. Our parametrization which is equivalent to the usual chiral description is the first general parametrization in the context of effective field theory in the ``quark" representation, where it has the minimal number of operators needed to describe all the octet and decuplet masses. We show that at two-loop level in the heavy-baryon chiral effective field theory, contributions of the three-body terms are cancelled and the general expression for baryon masses is reduced to the independent one- and two body operators. Our parametrization is particularly useful to an analysis of the baryon mass splittings due to both hypercharge-breaking and isospin-breaking effects. [Preview Abstract] |
Sunday, April 13, 2008 12:21PM - 12:33PM |
J11.00009: Relations Among Helicity Amplitudes for $2\longrightarrow 2$ Scattering in the Parke-Shadmi Spin Basis Gregory Mahlon When studying angular correlations in high energy scattering processes, it has proven fruitful to consider spin bases other than the traditional helicity basis in situations where the final state particles have significant masses (e.g. top quarks, electroweak gague bosons, Higgs bosons, etc.). We present differential identities connecting the helicity amplitudes for different total spin projections of the final state. These relations may be used as simple cross-checks of calculations of these amplitudes or as a means of deriving additional amplitudes, bypassing the need to calculate the entire set of amplitudes for a specific process explicitly. [Preview Abstract] |
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