Bulletin of the American Physical Society
2006 73rd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 9–11, 2006; Williamsburg, Virginia
Session MC: High Energy Physics II |
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Chair: Simonetta Liuti, University of Virginia Room: Williamsburg Hospitality House Empire C |
Saturday, November 11, 2006 8:30AM - 8:42AM |
MC.00001: Status of the ATLAS Transitional Radiation Tracker Richard Wall The ATLAS Transition Radiation Tracker (TRT) is a straw tube tracking system, which, together with the silicon tracking system, will provide precision measurements of particle tracks that are crucial for the discovery potential of the ATLAS detector at the Large Hadron Collider (LHC). Here we will overview the status of the TRT integration and commissioning, and discuss results on its alignment and tracking efficiency using recent cosmic-ray data. This understanding is important for optimizing the tracking and particle identification capabilities of the TRT for when physics results are expected in late 2007. [Preview Abstract] |
Saturday, November 11, 2006 8:42AM - 8:54AM |
MC.00002: Calibration, Installation {\&} Commissioning of Sensors for the Alignment of Muon Endcap Chambers in the CMS Experiment Samir Guragain, Marcus Hohlmann The positions of muon endcap chambers are to be monitored precisely in the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) by using analog sensors (R sensors, Z sensors, proximity sensors, and inclinometers) and optical DCOP sensors based on CCDs. The analog sensors were calibrated at Florida Tech using a semi-automated mechanical calibration bench and a Labview-based control and readout system. In summer 2006, half of all the sensors and readout were installed and commissioned on four endcap layers. Lasers beams were carefully adjusted for passage through all DCOPS on 15m Straight Line Monitors (SLM) across three endcap disks. During the summer, the detector was closed up and the huge 4 Tesla solenoid magnet of CMS was turned on for the first time ever. The movement of muon chambers for the alignment in R-{\O} and Z directions was monitored continuously by a complex system of wire extension and linear motion potentiometers, inclinometers, and DCOPS during the CMS Magnet Test {\&} Cosmic Challenge in the summer. Sensors clearly indicated the flexing of the large absorber disks when the field was turned on. We present sensor calibration methods and results, an overview of the installed sensor system, and first commissioning results for the endcap alignment at CERN. Supported by Florida Tech, Fermilab and Department of Energy. [Preview Abstract] |
Saturday, November 11, 2006 8:54AM - 9:06AM |
MC.00003: Muon Ionization Cooling for an 8 TeV Lepton Collider Don Summers A scenario for cooling muon bunches a factor of a million will be presented. Such cold muon bunches are the key to building an 8 TeV $\mu^+ \mu^-$ lepton collider to explore the energy frontier. Ionization in hydrogen slows muons in all directions. RF cavities add momentum back in just one direction. Steps involved include a straight ionization/RF channel for initial transverse cooling, a {\it Guggenheim} spiral for 6D cooling, a slip stacking ring for bunch coalesance, two 6D ionization cooling rings, and a final straight transverse cooling channel employing 50 Tesla BSCCO superconducting solenoids filled with liquid hydrogen. A two megawatt proton source ($p \to \pi \to \mu$) appears to be adequate to provide high luminosity for a $\mu^+ \mu^-$ collider. A program to learn how to build 50 Tesla solenoids has commenced at Fermilab. Other labs and universities are collaborating. Currently, 25 Tesla solenoids have been built. The current carrying capacity of BSCCO has been measured to be 266 Amps/mm$^2$ at 45 Tesla and 4$^0$\,K in Florida. [Preview Abstract] |
Saturday, November 11, 2006 9:06AM - 9:18AM |
MC.00004: The MiniBooNE event reconstruction and particle identification Denis Perevalov The MiniBooNE event reconstruction and particle identification are described. The related light model, input parameters and likelihood methods used in the event reconstruction, as well as the boosted decision trees algorithms advocated in the particle identification are explained. [Preview Abstract] |
Saturday, November 11, 2006 9:18AM - 9:30AM |
MC.00005: Three flavor neutrino oscillation analysis of atmospheric neutrinos in Super-Kamiokande Roger Wendell The nature of the neutrino mass hierarchy and the possibility of a nonzero $\theta_{13}$ are open problems in neutrino physics that can be probed by extending the standard two-flavor neutrino oscillation scenario to include all active flavors. In a three-flavor oscillation scheme there is known resonant enhancement (suppression) of the $\nu_{\mu} \rightarrow \nu_{e}$ transition probability in matter for several GeV neutrinos at long baselines for a normal (inverted) hierarchy when $\theta_{13} > 0 $. This effect is not present for the corresponding anti-neutrino transition. The Super-Kamiokande I atmospheric data has been analyzed using a three-flavor model testing both the normal and inverted mass hierarchies and has found no significant change in flux in its enriched multi-GeV $\nu_{\mu} $ or $\nu_{e}$ samples. Accordingly, confidence intervals for the atmospheric oscillation parameters have been obtained, the best fits being consistent with previous atmospheric results and zero $\theta_{13} $ for both hierarchies. [Preview Abstract] |
Saturday, November 11, 2006 9:30AM - 9:42AM |
MC.00006: Parameterization of Parton Distributions Functions Based on Self-Organizing Maps Y. Loitiere, H. Honkanen, S. Liuti Neural network algorithms have been recently applied to construct Parton Distribution Functions (PDFs) parametrizations which provide an alternative to standard global fitting procedures [1]. In this contribution we propose a different technique, namely an interactive neural network algorithm using Self-Organizing Maps (SOMs) [2]. SOMs generate a nonuniform projection from a high dimensional data space onto a low dimensional one (usually 1 or 2 dimensions) by clustering similar PDF representations together. Our SOMs are trained on progressively narrower selections of data samples. The selection criterion is that of convergence towards a neighborhood of the experimental data. Our procedure utilizes all available data on deep inelastic scattering in the kinematical region of 0.001 $\leq x \leq$ 0.75, and 1 $\leq Q^2 \leq$ 100 GeV$^2$, with a cut on the final state invariant mass, W$^2 \geq$ 10 GeV$^2$. Our main goal is to provide a fitting procedure that, at variance with standard neural network approaches, allows for an increased control of the systematic bias. SOMs, in fact, enable the user to directly control the data selection procedure at various stages of the process. \newline \newline [1] L. Del Debbio, S. Forte, J. I. Latorre, A. Piccione and J. Rojo, [NNPDF Collaboration], JHEP \textbf{0503}, 080 (2005). \newline [2] T. Kohonen, ``Self Organizing Maps,'' Springer-Verlag, 1997. [Preview Abstract] |
Saturday, November 11, 2006 9:42AM - 9:54AM |
MC.00007: Studying the Phase-Space Structure of Nucleons Using Generalized Parton Distributions Saeed Ahmad, Simonetta Liuti, Heli Honkanen, Swadhin K. Taneja We study the correlation of momentum and coordinate space distributions of partons which are measured in Deeply Virtual Compton Scattering (DVCS) reactions. Being able to understand the phase-space distributions of quarks, we hope to look into the question of `how much quark orbital angular momentum contributes towards the nucleon spin?' It was in fact suggested recently [1] that using the information provided by DVCS experiments, one can develop a complete three dimensional spatial picture of nucleons, along with the momentum distributions (the so-called Wigner distributions). However, in order pin down the spatial distribution in the longitudinal direction one has to take into account the constraint imposed by the uncertainty principle. In addition, similarly to inclusive deep-inelastic scattering, the lectromagnetic probe has an extended length in the longitudinal direction, known in the literature as ``Ioffe time'' [2]. Using the Generalized Parton Distributions (GPDs) obtained in [3] we define and evaluate ``Generalized Ioffe time'' distributions as a function of the additional degrees of freedom--both transverse, $t = -\Delta^2$ and longitudinal, $\xi$--extracted from DVCS experiments. [1] A. V. Belitsky, X. d. Ji and F. Yuan, Phys. Rev. D \textbf{69}, 074014 (2004) [2] B. L. Ioffe, Phys. Lett. B \textbf{30}, 123 (1969); V. Del Duca, S. J. Brodsky and P. Hoyer, Phys. Rev. D \textbf{46}, 931 (1992); V. Braun, P. Gornicki and L. Mankiewicz, Phys. Rev. D \textbf{51}, 6036 (1995). [3] S. Liuti and S. K. Taneja, Phys. Rev. D \textbf{70}, 074019 (2004); H. Honkanen, S. K. Taneja, S. Ahmad and S. Liuti, \textit{in preparation}. [Preview Abstract] |
Saturday, November 11, 2006 9:54AM - 10:06AM |
MC.00008: New Parametrization for Generalized Parton Distributions with Non-Zero Skewedness Heli Honkanen, Swadhin K. Taneja, Saeed Ahmad, Simonetta Liuti We present a physically motivated parameterization for the unpolarized generalized parton distributions of the nucleon, $H(X,\zeta,t$) and $E(X,\zeta,t)$, obtained from Deeply Virtual Compton Scattering (DVCS) experiments, where $X$ is the struck parton's momentum fraction, $\zeta$, skewedness parameter, is the fraction of longitudinal momentum transfer between the incoming (virtual) photon and the outgoing photon, and $t$ is the four-momentum transfer squared. At variance with other physically constrained parametrizations available in the literature [1,2], ours is the first one that applies to both zero and non-zero values of the skewedness parameter, $\zeta$. We define $H$ and $E$ using overlap integrals of the nucleon light-cone wave functions at large values of $X$ [3], and assuming Regge behavior at low $X$. At $\zeta$ = 0 we use the constraints provided by simultaneous fits to experimental data on both the elastic nucleon form factors and the ``forward'' parton distributions from deep inelastic scattering. Our results at $\zeta$ = 0 are of the same quality of the ones obtained in [1,2]. In order to extend our parametrization to $\zeta \neq$ 0, we work out additional constraints from recent lattice calculations of higher moments of generalized parton distributions [4]. [1] M. Diehl, T. Feldmann, R. Jakob and P. Kroll, Eur. Phys. J. C \textbf{39}, 1 (2005) [2] M. Guidal, M. V. Polyakov, A. V. Radyushkin and M. Vanderhaeghen, Phys. Rev. D \textbf{72}, 054013 (2005) [3] S. J. Brodsky, M. Diehl and D. S. Hwang, Nucl. Phys. B \textbf{596}, 99 (2001) [4] G. Schierholz and J. Zanotti, \textit{private communication}. [Preview Abstract] |
Saturday, November 11, 2006 10:06AM - 10:18AM |
MC.00009: Leptonic Structure Functions of Photons Klaus Dehmelt, Laszlo Baksay, Marcus Hohlmann Virtual photons can fluctuate into diverse final states. This can be described in terms of structure functions for photons. Among other processes, such fluctuations can yield muon-pairs. Apart from supplying another test of QED, purely leptonic processes provide a calibration for the hadronic processes. We report on a measurement with single-tagged two photon events from the LEP experiment L3, at c.m.s. energies between 189 GeV and 206 GeV. An overview of the fundamental physical processes and a discussion of the structure function results will be presented. [Preview Abstract] |
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