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Lattice of the NICA Collider Rings

Description: The Nuclotron-based Ion Collider fAcility (NICA) is a new accelerator complex being constructed at JINR. It is designed for collider experiments with ions and protons and has to provide ion-ion (Au{sup 79+}) and ion-proton collisions in the energy range 1 {divided_by} 4.5 GeV/n and collisions of polarized proton-proton and deuteron-deuteron beams. Collider conceptions with constant {gamma}{sub tr} and with possibility of its variation are considered. The ring has the racetrack shape with two arcs and two long straight sections. Its circumference is about 450m. The straight sections are optimized to have {beta}* {approx} 35cm in two IPs and a possibility of final betatron tune adjustment.
Date: May 1, 2010
Creator: Sidorin, Anatoly; /Dubna, JINR; Kozlov, Oleg; /Dubna, JINR; Meshkov, Igor; /Dubna, JINR et al.
Partner: UNT Libraries Government Documents Department

Superfluid helium testing of a stainless steel to titanium piping transition joint

Description: Stainless steel-to-titanium bimetallic transitions have been fabricated with an explosively bonded joint. This novel joining technique was conducted by the Russian Federal Nuclear Center, working under contract for the Joint Institute for Nuclear Research. These bimetallic transitions are being considered for use in future superconducting radio-frequency cavity cryomodule assemblies. This application requires cryogenic testing to demonstrate that this transition joint remains leak-tight when sealing superfluid helium. To simulate a titanium cavity vessel connection to a stainless steel service pipe, bimetallic transition joints were paired together to fabricate piping assemblies. These piping assemblies were then tested in superfluid helium conditions at Fermi National Accelerator Laboratory test facilities. The transition joint test program will be described. Fabrication experience and test results will be presented.
Date: November 1, 2009
Creator: Soyars, W.; /Fermilab; Basti, A.; Bedeschi, F.; /INFN, Pisa; Budagov, J. et al.
Partner: UNT Libraries Government Documents Department

Muon collider interaction region design

Description: Design of a muon collider interaction region (IR) presents a number of challenges arising from low {beta}* < 1 cm, correspondingly large beta-function values and beam sizes at IR magnets, as well as the necessity to protect superconducting magnets and collider detectors from muon decay products. As a consequence, the designs of the IR optics, magnets and machine-detector interface are strongly interlaced and iterative. A consistent solution for the 1.5 TeV c.o.m. muon collider IR is presented. It can provide an average luminosity of 10{sup 34} cm{sup -2}s{sup -1} with an adequate protection of magnet and detector components.
Date: May 1, 2010
Creator: Alexahin, Y.I.; Gianfelice-Wendt, E.; Kashikhin, V.V.; Mokhov, N.V.; Zlobin, A.V.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Evidence for production of single top quarks

Description: We present first evidence for the production of single top quarks in the D0 detector at the Fermilab Tevatron p{bar p} collider. The standard model predicts that the electroweak interaction can produce a top quark together with an antibottom quark or light quark, without the antiparticle top quark partner that is always produced from strong coupling processes. Top quarks were first observed in pair production in 1995, and since then, single top quark production has been searched for in ever larger datasets. In this analysis, we select events from a 0.9 fb{sup -1} dataset that have an electron or muon and missing transverse energy from the decay of a W boson from the top quark decay, and two, three, or four jets, with one or two of the jets identified as originating from a b hadron decay. The selected events are mostly backgrounds such as W+jets and t{bar t} events, which we separate from the expected signals using three multivariate analysis techniques: boosted decision trees, Bayesian neural networks, and matrix element calculations. A binned likelihood fit of the signal cross section plus background to the data from the combination of the results from the three analysis methods gives a cross section for single top quark production of {sigma}(p{bar p} {yields} tb + X, tqb + X) = 4.7 {+-} 1.3 pb. The probability to measure a cross section at this value or higher in the absence of signal is 0.014%, corresponding to a 3.6 standard deviation significance. The measured cross section value is compatible at the 10% level with the standard model prediction for electroweak top quark production. We use the cross section measurement to directly determine the Cabibbo-Kobayashi-Maskawa quark mixing matrix element that describes the Wtb coupling and find |V{sub tb}f{sub 1}{sup L}| = 1.31{sub -0.21}{sup +0.25}, where f{sub ...
Date: March 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Measurement of differential Z / gamma* + jet + X cross sections in p anti-p collisions at s**(1/2) = 1.96-TeV

Description: We present new measurements of differential cross sections for Z/{gamma}* ({yields} {mu}{mu})+jet+X production in a 1 fb{sup -1} data sample collected with the D0 detector in p{bar p} collisions at {radical}s = 1.96 TeV. Results include the first measurements differential in the Z/{gamma}* transverse momentum and rapidity, as well as new measurements differential in the leading jet transverse momentum and rapidity. Next-to-leading order perturbative QCD predictions are compared to the measurements, and reasonable agreement is observed, except in the region of low Z/{gamma}* transverse momentum. Predictions from two event generators based on matrix elements and parton showers, and one pure parton shower event generator are also compared to the measurements. These show significant overall normalization differences to the data and have varied success in describing the shape of the distributions.
Date: August 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Measurement of the forward-backward charge asymmetry and extraction of $sin^2Theta^{eff}_W$ in $p\bar{p} \to Z/\gamma^{*}+X \to e^+e^-+X$ events produced at $\sqrt{s}=1.96$ TeV

Description: We present a measurement of the forward-backward charge asymmetry (A{sub FB}) in p{bar p} {yields} Z/{gamma}* + X {yields} e{sup +}e{sup -} + X events at a center-of-mass energy of 1.96 TeV using 1.1 fb{sup -1} of data collected with the D0 detector at the Fermilab Tevatron collider. A{sub FB} is measured as a function of the invariant mass of the electron-positron pair, and found to be consistent with the standard model prediction. We use the A{sub FB} measurement to extract the effective weak mixing angle sin{sup 2} {theta}{sub W}{sup eff} = 0.2327 {+-} 0.0018 (stat.) {+-} 0.0006 (syst.).
Date: April 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for long-lived particles decaying into electron or photon pairs with the D0 detector

Description: In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, like hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark.
Date: June 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for the standard model Higgs boson in the ZH->vvbb channel in 5.2 fb-1 of p-pbar collisions at sqrt(s)=1.96 TeV

Description: A search is performed for the standard model Higgs boson in 5.2 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV, collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered is a pair of b jets and large missing transverse energy, as expected from p{bar p} {yields} ZH {yields} {nu}{bar {nu}}b{bar b} production. The search is also sensitive to the WH {yields} {ell}{nu}b{bar b} channel when the charged lepton is not identified. For a Higgs boson mass of 115 GeV, a limit is set at the 95% C.L. on the cross section multiplied by branching fraction for (p{bar p} {yields} (Z/W)H) x (H {yields} b{bar b}) that is a factor of 3.7 larger than the standard model value, consistent with the factor of 4.6 expected.
Date: December 1, 2009
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at s**(1/2) = 1.96-TeV

Description: The authors present the first simultaneous measurement of the ratio of branching fractions, R = {Beta}(t {yields} Wb)/{Beta}(t {yields} Wq), with q being a d, s, or b quark, and the top quark pair production cross section {sigma}{sub t{bar t}} in the lepton plus jets channel using 0.9 fb{sup -1} of p{bar p} collision data at {radical}s = 1.96 TeV collected with the D0 detector. they extract R and {sigma}{sub t{bar t}} by analyzing samples of events with 0, 1 and {ge} 2 identified b jets. They measure R = 0.97{sub -0.08}{sup +0.09} (stat+syst) and {sigma}{sub t{bar t}} = 8.18{sub -0.84}{sup +0.90}(stat+syst) {+-} 0.50 (lumi) pb, in agreement with the standard model prediction.
Date: January 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Measurement of the polarization of the $\Upsilon(1S)$ and $\Upsilon(2S)$ states in $p\bar{p}$ collisions at $\sqrt{s}=$1.96 TeV

Description: We present a study of the polarization of the {Upsilon}(1S) and {Upsilon}(2S) states using a 1.3 fb{sup -1} data sample collected by the D0 experiment in 2002-2006 during Run II of the Fermilab Tevatron Collider. We measure the polarization parameter {alpha} = ({sigma}{sub T} - 2{sigma}{sub L})/({sigma}{sub T} + 2{sigma}{sub L}), where {sigma}{sub T} and {sigma}{sub L} are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum (p{sub T}{sup {Upsilon}}) for the {Upsilon}(1S) and {Upsilon}(2S). Significant p{sub T}{sup {Upsilon}}-dependent longitudinal polarization is observed for the {Upsilon}(1S). A comparison with theoretical models is presented.
Date: April 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Study of direct CP violation in B+- ---> J/psi K+- (pi+-) file decays

Description: The authors present a search for direct CP violation in B{sup {+-}} {yields} J/{psi}K{sup {+-}}{pi}{sup {+-}} decays. The event sample is selected from 2.8 fb{sup -1} of p{bar p} collisions recorded by D0 experiment in Run II of the Fermilab Tevatron Collider. The charge asymmetry A{sub CP}(B{sup +} {yields} J/{psi}K{sup +}) = +0.0075 {+-} 0.0061(stat.) {+-} 0.0027(syst.) is obtained using a sample of approximately 40 thousand B{sup {+-}} {yields} J/{psi}K{sup {+-}} decays. The achieved precision is of the same level as the expected deviation predicted by some extensions of the standard model. They also measured the charge asymmetry A{sub CP}(B{sup +} {yields} J/{psi}{pi}{sup +}) = -0.09 {+-} 0.08(stat.){+-}0.03(syst.).
Date: February 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for large extra dimensions in the mono-photon final state at s**(1/2) = 1.96-TeV

Description: The authors report on a search for large extra dimensions in a data sample of approximately 1 fb{sup -1} of p{bar p} collisions at {radical}s = 1.96 TeV. They investigate Kaluza-Klein graviton production with a photon and missing transverse energy in the final state. At the 95% C.L. they set limits on the fundamental mass scale M{sub D} from 884 GeV to 778 GeV for 2 to 8 extra dimensions.
Date: March 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Search for a Higgs boson produced in association with a Z boson in p anti-p collisions

Description: We describe a search for the standard model Higgs boson with a mass of 105 GeV/c{sup 2} to 145 GeV/c{sup 2} in data corresponding to an integrated luminosity of approximately 450 pb{sup -1} collected with the D0 detector at the Fermilab Tevatron p{bar p} collider at a center-of-mass energy of 1.96 TeV. The Higgs boson is required to be produced in association with a Z boson, and the Z boson is required to decay to either electrons or muons with the Higgs boson decaying to a b{bar b} pair. The data are well described by the expected background, leading to 95% confidence level cross section upper limits {sigma}p{bar p} {yields} ZH x B(H {yields} b{bar b}) in the range of 3.1 pb to 4.4 pb.
Date: April 1, 2007
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department

Measurement of B0(s) mixing parameters from the flavor-tagged decay B0(s) ---> J/psi phi

Description: From an analysis of the flavor-tagged decay B{sub s}{sup 0} {yields} J/{psi}{phi} they obtain the width difference between the B{sub s}{sup 0} light and heavy mass eigenstates, {Delta}{Lambda}{sub s} {triple_bond} {Lambda}{sub L} - {Lambda}{sub H} = 0.19 {+-} 0.07(stat){sub -0.01}{sup +0.02}(syst) ps{sup -1}, and the CP-violating phase, {phi}{sub s} = -0.57{sub -0.30}{sup +0.24}(stat){sub -0.02}{sup +0.07}(syst). The allowed 90% C.L. intervals of {Delta}{Lambda}{sub s} and {phi}{sub s} are 0.06 < {Delta}{Lambda}{sub s} < 0.30 ps{sup -1} and -1.20 < {phi}{sub s} < 0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb{sup -1} accumulated with the D0 detector at the Fermilab Tevatron collider.
Date: February 1, 2008
Creator: Abazov, V.M.; /Dubna, JINR; Abbott, B.; U., /Oklahoma; Abolins, M.; U., /Michigan State et al.
Partner: UNT Libraries Government Documents Department