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The architecture of the BTeV pixel readout chip

Description: The most striking feature of BTeV, a dedicated b physics experiment which is expected to begin running in 2008 in the new CZero interaction region of the Fermilab Tevatron, is that the experiment will use data from a pixel vertex detector to reconstruct tracks and vertices for every beam crossing. The lowest level trigger will be an impact parameter trigger designed to identify events containing reconstructable decays of charm and bottom particles[1]. An R&D program to develop a pixel readout chip optimized for the Tevatron was started at Fermilab in 1997, and is now nearing completion. The architecture of the BTeV pixel readout chip is described in this paper.
Date: December 3, 2002
Creator: Christian, David C
Partner: UNT Libraries Government Documents Department


Description: Interactions between Ar projectiles and lead are studied in terms of global observables. The Streamer Chamber at the Berkeley BEVALAC was used to record all charged particles produced in collisions between 0.8 GeV/{mu} Ar projectiles with a Pb{sub 3}O{sub 4} target. A hardware trigger selected central collisions with PB nuclei corresponding to a trigger cross section of 1 barn. In a geometrical picture this is equivalent to an impact parameter range of 0--5 fm.
Date: August 1, 1983
Creator: Renfordt, R.E.
Partner: UNT Libraries Government Documents Department

Observation of Two-source Interference in the Photoproduction Reaction AuAu --> AuAu rho 0

Description: In ultra-peripheral relativistic heavy-ion collisions, a photon from the electromagnetic field of one nucleus can fluctuate to a quark-antiquark pair and scatter from the other nucleus, emerging as a {rho}{sup 0}. The {rho}{sup 0} production occurs in two well-separated (median impact parameters of 20 and 40 fermi for the cases considered here) nuclei, so the system forms a 2-source interferometer. At low transverse momenta, the two amplitudes interfere destructively, suppressing {rho}{sup 0} production. Since the {rho}{sup 0} decays before the production amplitudes from the two sources can overlap, the two-pion system can only be described with an entangled non-local wave function, and is thus an example of the Einstein-Podolsky-Rosen paradox. We observe this suppression in 200 GeV per nucleon-pair gold-gold collisions. The interference is 87% {+-} 5%(stat.) {+-} 8% (syst.) of the expected level. This translates into a limit on decoherence due to wave function collapse or other factors, of 23% at the 90% confidence level.
Date: March 2, 2009
Creator: Coll, STAR
Partner: UNT Libraries Government Documents Department

Comments on 'Modeling Galaxy Halos Using Dark Matter with Pressure'

Description: We comment on the calculational mistake in the paper 'Modeling galaxy halos using dark matter with pressure' by Somnath Bharadwaj and Sayan Kar. The authors made a mistake while calculating the metric, which led to an overestimate of the deflection angle of light passing through the halos for -1 < w{sub r} < -0.5 and an underestimate of the deflection angle for -0.5 < w{sub r} < 0. In addition, the solution for w{sub r} > 0 should not exist. Although the Bharadwaj-Kar solution should be corrected, it appears that the characteristics of the deflection angle under the supposed nonconventional, nonideal fluid equation of state for the dark matter halo remain sensitive to the impact parameter and may be verifiable through observations.
Date: November 30, 2011
Creator: Su, Kung-Yi; /Taiwan, Natl. Taiwan U.; Chen, Pisin & /Taiwan, Natl. Taiwan U. /KIPAC, Menlo Park /SLAC
Partner: UNT Libraries Government Documents Department

Performance and first physics results of the SVT trigger at CDF II

Description: For the first time in a hadron collider, a novel trigger processor, the Silicon Vertex Trigger (SVT), allows to select the long-lived heavy flavor particles by cutting on the track impact parameter with a precision similar to that of the offline reconstruction. Triggering on displaced tracks has enriched the B-physics program by enhancing the B yields of the lepton-based triggers and opened up full hadronic triggering at CDF. After a first commissioning period, the SVT is fully operational, performing very closely to its design capabilities. System performance and first physics results based on SVT selected data samples are presented.
Date: December 3, 2003
Creator: Vila, I.
Partner: UNT Libraries Government Documents Department

Deutron photodissociation in ultraperipheral relativistic heavyion on deutron collisions

Description: In ultraperipheral relativistic deuteron on heavy-ion collisions, a photon emitted from the heavy nucleus may dissociate the deuterium ion. We find deuterium breakup cross sections of 1.24 barns for deuterium-gold collisions at a center of mass energy of 200 GeV per nucleon, as studied at the Relativistic Heavy Ion Collider, and 2.35 barns for deuterium-lead collisions at a center of mass energy of 6.2 TeV, as proposed for the Large Hadron Collider. In the latter case, the cross section is as large as that of hadronic interactions. The estimated error is 5%. We discuss the use of this process as a luminosity monitor and a 'tag' for moderate impact parameter collisions.
Date: March 24, 2003
Creator: Klein, Spencer & Vogt, Ramona
Partner: UNT Libraries Government Documents Department

Global quark polarization in non-central A+A collisions

Description: Partons produced in the early stage of non-central heavy-ioncollisionscan develop a longitudinal fluid shear because of unequal localnumber densities of participant target and projectile nucleons. Undersuch fluid shear, local parton pairs with non-vanishing impact parameterhave finite local relative orbital angular momentum along the directionopposite to the reaction plane. Such finite relative orbitalangularmomentum among locally interacting quark pairs can lead to global quarkpolarization along the same direction due to spin-orbital coupling. Locallongitudinal fluid shear is estimated within both Landau fireball andBjorken scaling model of initial parton production. Quark polarizationthrough quark-quark scatterings with the exchange of a thermal gluon iscalculated beyond small-angle scattering approximation in a quark-gluonplasma. The polarization is shown to have a non-monotonic dependence onthe local relative orbital angular momentum dictated by the interplaybetween electric and magnetic interaction. It peaks at a value ofrelative orbital angular momentum which scales with the magnetic mass ofthe exchanged gluons. With the estimated small longitudinal fluid shearin semi-peripheral Au+Au collisions at the RHIC energy, the final quarkpolarization is found to be small left hbar P_q right hbar<0.04 inthe weak coupling limit. Possible behavior of the quark polarization inthe strong coupling limit and implications on the experimental detectionof such global quark polarization at RHIC and LHC are alsodiscussed.
Date: October 12, 2007
Creator: Gao, Jian-Hua; Chen, Shou-Wan; Deng, Wei-tian; Tang, Zuo-Tang; Wang, Qun & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data

Description: New transiting planet candidates are identified in sixteen months (May 2009 - September 2010) of data from the Kepler spacecraft. Nearly five thousand periodic transit-like signals are vetted against astrophysical and instrumental false positives yielding 1091 viable new planet candidates, bringing the total count up to over 2,300. Improved vetting metrics are employed, contributing to higher catalog reliability. Most notable is the noise-weighted robust averaging of multiquarter photo-center offsets derived from difference image analysis which identifies likely background eclipsing binaries. Twenty-two months of photometry are used for the purpose of characterizing each of the new candidates. Ephemerides (transit epoch, T{sub 0}, and orbital period, P) are tabulated as well as the products of light curve modeling: reduced radius (R{sub P}/R{sub {star}}), reduced semi-major axis (d/R{sub {star}}), and impact parameter (b). The largest fractional increases are seen for the smallest planet candidates (197% for candidates smaller than 2R{sub {circle_plus}} compared to 52% for candidates larger than 2R{sub {circle_plus}}) and those at longer orbital periods (123% for candidates outside of 50 day orbits versus 85% for candidates inside of 50 day orbits). The gains are larger than expected from increasing the observing window from thirteen months (Quarter 1 - Quarter 5) to sixteen months (Quarter 1 - Quarter 6). This demonstrates the benefit of continued development of pipeline analysis software. The fraction of all host stars with multiple candidates has grown from 17% to 20%, and the paucity of short-period giant planets in multiple systems is still evident. The progression toward smaller planets at longer orbital periods with each new catalog release suggests that Earth-size planets in the Habitable Zone are forthcoming if, indeed, such planets are abundant.
Date: February 1, 2012
Creator: Batalha, Natalie M.; U., /San Jose State; Rowe, Jason F.; /NASA, Ames; Bryson, Stephen T.; /NASA, Ames et al.
Partner: UNT Libraries Government Documents Department

Di-J/psi Studies, Level 3 Tracking and the D0 Run IIb Upgrade

Description: The D0 detector underwent an upgrade to its silicon vertex detector and triggering systems during the transition from Run IIa to Run IIb to maximize its ability to fully exploit Run II at the Fermilab Tevatron. This thesis describes improvements made to the tracking and vertexing algorithms used by the high level trigger in both Run IIa and Run IIb, as well as a search for resonant di-J/{psi} states using both Run IIa and Run IIb data. Improvements made to the tracking and vertexing algorithms during Run IIa included the optimization of the existing tracking software to reduce overall processing time and the certification and testing of a new software release. Upgrades made to the high level trigger for Run IIb included the development of a new tracking algorithm and the inclusion of the new Layer 0 silicon detector into the existing software. The integration of Layer 0 into the high level trigger has led to an improvement in the overall impact parameter resolution for tracks of {approx}50%. The development of a new parameterization method for finding the error associated to the impact parameter of tracks returned by the high level tracking algorithm, in association with the inclusion of Layer 0, has led to improvements in vertex resolution of {approx}4.5 {micro}m. A previous search in the di-J/{psi} channel revealed a unpredicted resonance at {approx}13.7 GeV/c{sup 2}. A confirmation analysis is presented using 2.8 fb{sup -1} of data and two different approaches to cuts. No significant excess is seen in the di-J/{psi} mass spectrum.
Date: October 1, 2009
Creator: Vint, Philip John & /Imperial Coll., London
Partner: UNT Libraries Government Documents Department

Considerations on ODR beam-size monitoring for gamma = 1000 beams

Description: We discuss the feasibility of monitoring the beam size of {gamma} = 1000 beams with 3000 times more charge in a video frame time and with a more sensitive 12- to 16-bit camera than were used in the previous electron beam studies at 7 GeV at the Advanced Photon Source. Such a beam would be generated at Fermilab in a new facility in the coming years. Numerical integrations of our base model show beam size sensitivity for {+-} 20% level changes at 200- and 400-{micro}m base beam sizes. We also evaluated impact parameters of 5 {sigma}{sub y} and 12 {sigma}{sub y} for both 800-nm and 10-{micro}m observation wavelengths. The latter examples are related to a proposal to apply the technique to an {approx}0.98 TeV proton beam, and this study shows there are trades on photon intensity and beam size sensitivity to be considered at such gammas. In addition, we report on first results at {gamma} = 1800 on a superconducting rf linac.
Date: April 1, 2008
Creator: Lumpkin, A.H.; /Fermilab; Yao, C.-Y.; /Argonne; Chiadroni, E.; Castellano, M. et al.
Partner: UNT Libraries Government Documents Department

Decay Properties of p pi- Systems Produced in Neutron Dissociation at Fermilab Energies

Description: The authors have examined the decay distributions of (p{pi}{sup -}) systems produced in the reaction n + p {yields} (p{pi}{sup -}) + p for neutron momenta between 120 GeV/c and 300 GeV/c. Preliminary analysis of decay moments indicates the presence of large helicity-flip amplitudes even for small (p{pi}{sup -}) mass values, and does not support the hypothesis that the helicity non-flip (p{pi}{sup -}) states are produced peripherally in impact parameter. These results are in approximate agreement with predictions of the Deck mechanism. The experiment was performed at the M-3 neutral beam of Fermilab.
Date: June 1, 1975
Creator: Biel, J.; U., /Rochester; Bleser, E.J.; /Fermilab; Duke, D.; Ferbel, T. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the $B^-$ lifetime using a simulation free approach for trigger bias correction

Description: The collection of a large number of B hadron decays to hadronic final states at the CDF II detector is possible due to the presence of a trigger that selects events based on track impact parameters. However, the nature of the selection requirements of the trigger introduces a large bias in the observed proper decay time distribution. A lifetime measurement must correct for this bias and the conventional approach has been to use a Monte Carlo simulation. The leading sources of systematic uncertainty in the conventional approach are due to differences between the data and the Monte Carlo simulation. In this paper they present an analytic method for bias correction without using simulation, thereby removing any uncertainty between data and simulation. This method is presented in the form of a measurement of the lifetime of the B{sup -} using the mode B{sup -} {yields} D{sup 0}{pi}{sup -}. The B{sup -} lifetime is measured as {tau}{sub B{sup -}} = 1.663 {+-} 0.023 {+-} 0.015 ps, where the first uncertainty is statistical and the second systematic. This new method results in a smaller systematic uncertainty in comparison to methods that use simulation to correct for the trigger bias.
Date: April 1, 2010
Creator: Aaltonen, T.; Phys., /Helsinki Inst. of; Adelman, J.; /Chicago U., EFI; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of et al.
Partner: UNT Libraries Government Documents Department

Silicon vertex tracker: A fast precise tracking trigger for CDF

Description: The Silicon Vertex Tracker (SVT), currently being built for the CDF II experiment, is a hardware device that reconstructs 2-D tracks online using measurements from the Silicon Vertex Detector (SVXII) and the Central Outer Tracker (COT). The precise measurement of the impact parameter of the SVT tracks will allow, for the first time in a hadron collider environment, to trigger on events containing B hadrons that are very important for many studies, such as CP violation in the b sector and searching for new heavy particles decaying to b{bar b}. In this report we describe the overall architecture, algorithms and the hardware implementation of the SVT.
Date: October 7, 1999
Creator: others], W. Ashmanskas
Partner: UNT Libraries Government Documents Department


Description: High-energy collisions of heavy ions provide a means to study QCD in a regime of high parton density, and may provide insight into its phme structure. Results from the four experiments at RHIC (BRAHMS, PHENIX, PHOBOS and STAR) are presented, and placed in context with the lower energy data from the AGS and SPS accelerators. The focus is on the insights these measurements provide into the time history of the collision process. Taken together, the data point to the creation of a deconfined state of matter that forms quickly, expands rapidly and freezes out suddenly. With the new RHIC data, systematic data now exists for heavy ion collisions as a function of {radical}s over several orders of magnitude and as a function of impact parameter. These data test the interplay between hard and soft processes in a large-volume system where nucleons are struck multiple times. The data is consistent with creating a deconfined state (jet quenching) that forms quickly (saturation models), expands rapidly (radial and elliptic flow) and freezes out suddenly (single freezeout and blast wave fits). There are also intriguing connections with particle production in elementary systems, which point to the role of the energy available for particle production on the features of the final state. Many in this field are optimistic that the careful understanding of this experimental data may lead t o the theoretical breakthroughs that will connect these complex systems to the fundamental lattice predict ions.
Date: June 20, 2002
Partner: UNT Libraries Government Documents Department

The CDF silicon vertex trigger

Description: The CDF experiment's Silicon Vertex Trigger is a system of 150 custom 9U VME boards that reconstructs axial tracks in the CDF silicon strip detector in a 15 {mu}sec pipeline. SVT's 35 {mu}m impact parameter resolution enables CDF's Level 2 trigger to distinguish primary and secondary particles, and hence to collect large samples of hadronic bottom and charm decays. We review some of SVT's key design features. Speed is achieved with custom VLSI pattern recognition, linearized track fitting, pipelining, and parallel processing. Testing and reliability are aided by built-in logic state analysis and test-data sourcing at each board's input and output, a common inter-board data link, and a universal ''Merger'' board for data fan-in/fan-out. Speed and adaptability are enhanced by use of modern FPGAs.
Date: June 23, 2003
Creator: Ashmanskas, B.; Barchiesi, A. & Bardi, A.
Partner: UNT Libraries Government Documents Department


Description: Coherent vector meson production in peripheral nucleus-nucleus collisions is discussed. These interactions may occur for impact parameters much larger than the sum of the nuclear radii. Since the vector meson production is always localized to one of the nuclei, the system acts as a two-source interferometer in the transverse plane. By tagging the outgoing nuclei for Coulomb dissociation it is possible to obtain a measure of the impact parameter and thus the source separation in the interferometer. This is of particular interest since the life-time of the vector mesons are generally much shorter than the impact parameters of the collisions.
Date: October 16, 2002
Creator: Nystrand, J.; Baltz, A. J. & Klein, S. R.
Partner: UNT Libraries Government Documents Department

Energy losses of channeled ions: the BOHR theory revisited. [Impact parameter]

Description: Theoretical models are presented based on the impact parameter picture for the energy losses of channeled ions. The conceptual simplicity afforded by such an approach is quite appealing. In addition, it is found that calculations based on these models provide reasonable predictions for, and agreement with, a variety of experimental data. A useful approach is provided for meeting the challenges to theory afforded by experimental measurements on channeling phenomena.
Date: January 1, 1977
Creator: Ashley, J C & Ritchie, R H
Partner: UNT Libraries Government Documents Department

Physics of Ultra-Peripheral Nuclear Collisions

Description: Moving highly-charged ions carry strong electromagnetic fields which act as a field of photons. In collisions at large impact parameters, hadronic interactions are not possible, and the ions interact through photon-ion and photon-photon collisions known as ultra-peripheral collisions (UPC). Hadron colliders like the Relativistic Heavy Ion Collider (RHIC), the Tevatron and the Large Hadron Collider (LHC) produce photonuclear and two-photon interactions at luminosities and energies beyond that accessible elsewhere; the LHC will reach a {gamma}p energy ten times that of the Hadron-Electron Ring Accelerator (HERA). Reactions as diverse as the production of anti-hydrogen, photoproduction of the {rho}{sup 0}, transmutation of lead into bismuth and excitation of collective nuclear resonances have already been studied. At the LHC, UPCs can study many types of ''new physics''.
Date: February 2, 2005
Creator: Bertulani, Carlos A.; Klein, Spencer R. & Nystrand, Joakim
Partner: UNT Libraries Government Documents Department

Long-term Running Experience with the Silicon Micro-strip Tracker at the D{\O} detector

Description: The Silicon Micro-strip Tracker (SMT) at the D0 experiment in the Fermilab Tevatron collider has been operating since 2001. In 2006, an additional layer, referred to as 'Layer 0', was installed to improve impact parameter resolution and compensate for detector degradation due to radiation damage to the original innermost SMT layer. The SMT detector provides valuable tracking and vertexing information for the experiment. This contribution will highlight aspects of the long term operation of the SMT, including the impact of the silicon readout test-stand. Due to the full integration of the test-stand into the D0 trigger framework, this test-stand provides an advantageous tool for training of new experts and studying subtle effects in the SMT while minimizing impact on the global data acquisition.
Date: February 1, 2012
Creator: Jung, Andreas W.; Cherry, M.; Edmunds, D.; Johnson, M.; Matulik, M.; Utes, M. et al.
Partner: UNT Libraries Government Documents Department

Multi-muon events at CDF

Description: We report a study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDF II detector. In a data set acquired with a dedicated dimuon trigger and corresponding to an integrated luminosity of 2100 pb{sup -1}, we isolate a significant sample of events in which at least one of the identified muons has large impact parameter and is produced outside the beam pipe of radius 1.5 cm. We are unable to fully account for the number and properties of the events through standard model processes in conjunction with our current understanding of the CDF II detector, trigger and event reconstruction. Several topological and kinematic properties of these events are also presented. In contrast, the production cross section and kinematics of events in which both muon candidates are produced inside the beam pipe are successfully modeled by known QCD processes which include heavy flavor production. The presence of these anomalous multi-muon events offers a plausible resolution to long-standing inconsistencies related to b{bar b} production and decay.
Date: July 1, 2009
Creator: Ptochos, F. & U., /Cyprus
Partner: UNT Libraries Government Documents Department

Search for the Standard Model Higgs boson in the missing energy topology with D0

Description: A search for the Standard Model Higgs boson in the missing energy and acoplanar b-jet topology is reported, using an integrated luminosity of 0.93 fb{sup -1} recorded by the D0 detector at the Fermilab Tevatron p{bar p} Collider. The analysis includes signal contributions from p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b}, as well as from WH production in which the charged lepton from the W boson decay is undetected. Neural networks are used to separate signal from background. In the absence of a signal, limits are set on {sigma}(p{bar p} {yields} VH) x B(H {yields} b{bar b}) at the 95% C.L. of 2.6-2.3 pb, for Higgs boson masses in the range 105-135 GeV, where V = W, Z. The corresponding expected limits range from 2.8 to 2.0 pb. Potential improvements to the analysis with an extended dataset totalling 4 fb{sup -1} are also discussed. Essential maintenance related to the increased luminosity and RunIIb upgrade was carried out on the impact parameter (IP) based b-tagging trigger tool and the effect of the changes on the b-tagger's performance was investigated.
Date: June 1, 2009
Creator: Christoudias, Theodoros & /Imperial Coll., London
Partner: UNT Libraries Government Documents Department

Measurement of the polarization amplitudes of the Bs -> PhiPhi decay at CDF II

Description: In this thesis we present the first measurement of the polarization amplitudes for the charmless B{sub s} {yields} {phi}{phi} {yields} [K{sup +}K{sup -}][K{sup +}K{sup -}] decay of the B{sub s} meson. The result is achieved using an unbinned Maximum Likelihood fit to the data collected by the Collider Detector at Fermilab (CDF) in Run II (CDFII), in a period starting from March 2001 till April 2008, which corresponds to an integrated luminosity of 2.9 fb{sup -1}. The resulting yield consists of 300 signal events selected by the Two Track Trigger (TTT). Furthermore, our work puts in evidence an original topic, that was never observed until now: an unexpected dependence of the signal acceptance on the proper decay time (t) of the B{sub s} mesons. This specific issue, which is most likely a general feature induced by any signal selection based on the lifetime information, is supposed to be related to the on-line TTT and off-line selections based on the impact parameter. The involved fit, indeed, reproduces the biases observed in large statistics Monte Carlo (MC) samples. The thesis presents the same analysis performed for the B{sub s}{sup 0} {yields} J{psi}{phi} decay as well, which is used as a control sample. The polarizations amplitudes we find are consistent with the published ones; this result contributes to enforce the reliability of the analysis. This work is considered ready to begin the procedure for official approval by the CDF collaboration pending the finalization of the systematic uncertainty which has not yet been fully completed.
Date: October 1, 2009
Creator: Dorigo, Mirco & /Trieste U. /INFN, Trieste
Partner: UNT Libraries Government Documents Department

Measurement of the cp asymmetry in semimuonic b decays produced in ppbar collision at s**(1/2) = 1.96 TeV

Description: The authors measure the asymmetry between positive and negative same-sign muon pairs originating from semileptonic decays of pairs of B hadrons. Low transverse momentum dimuon pairs are evaluated to determine B hadron content using a log likelihood fit to two-dimensional impact parameter significance templates. Corrections are made for asymmetries arising from the detector, trigger, and hadrons which are reconstructed as muons. Using 1.1 million muon pairs from data corresponding to an integrated luminosity of 1.6 fb{sup -1}, they find 210,000 same-sign muon pairs with both muon candidates coming from B decays. After corrections, they measure a semileptonic asymmetry from neutral B mixing of A{sub SL} = 0.0080 {+-} 0.0090(stat) {+-} 0.0068(syst). This asymmetry can be interpreted as a constraint on the complex phase of the CKM matrix element V{sub ts} by using the B{sup 0} neutral mixing contribution measured at the B factories. They measure the CP violating asymmetry from B{sub s} mixing to be A{sub SL}{sup s} = 0.020 {+-} 0.028.
Date: December 1, 2007
Creator: Marino, Christopher Phillip & /Illinois U., Urbana
Partner: UNT Libraries Government Documents Department

Two-Photon Interactions with Nuclear Breakup in Relativistic Heavy Ion Collisions

Description: Highly charged relativistic heavy ions have high cross-sections for two-photon interactions. The photon flux is high enough that two-photon interactions may be accompanied by additional photonuclear interactions. Except for the shared impact parameter, these interactions are independent. Additional interactions like mutual Coulomb excitation are of experimental interest, since the neutrons from the nuclear dissociation provide a simple, relatively unbiased trigger. We calculate the cross sections, rapidity, mass and transverse momentum (p{sub T}) distributions for exclusive {gamma}{gamma} production of mesons and lepton pairs, and for {gamma}{gamma} reactions accompanied by mutual Coulomb dissociation. The cross-sections for {gamma}{gamma} interactions accompanied by multiple neutron emission (XnXn) and single neutron emission (1n1n) are about 1/10 and 1/100 of that for the unaccompanied {gamma}{gamma} interactions. We discuss the accuracy with which these cross-sections may be calculated. The typical p{sub T} of {gamma}{gamma} final states is several times smaller than for comparable coherent photonuclear interactions, so p{sub T} may be an effective tool for separating the two classes of interactions.
Date: July 7, 2010
Creator: Baltz, Anthony J.; Gorbunov, Yuri; R Klein, Spencer & Nystrand, Joakim
Partner: UNT Libraries Government Documents Department