1,119,925 research outputs found
Effects of soft gluon emission on the opposite-side acollinearity distributions in e+e- annihilation
No full textBaier R, Fey K. Effects of soft gluon emission on the opposite-side acollinearity distributions in e+e- annihilation. Nuclear physics B. 1981;179(1):49-61
Positronium Annihilation Lifetime Spectroscopy Study of SBA-15
No full textPositronium annihilation lifetime spectroscopy (PALS) is a technique used in the characterization of porosity in nanostructured materials. Positrons, the antiparticle to the electron, enter a sample and either immediately annihilate with an electron or they can capture an electron to form Positronium (Ps), the hydrogen-like bound state. Ps then annihilates with a lifetime corresponding to the pore size. This annihilation converts the total mass of the positron and electron into high-energy photons. These annihilations are detected to measure Positronium lifetime. SBA-15, a mesoporous silica that consists of a two dimensional hexagonal array of cylindrical mesopores with interconnecting micropores, is a system of interest as a catalysis support and low- dielectric constant material. Nitrogen adsorption, x-ray diraction, and small angle neutron scattering (SANS) have been used to characterize the pore structure in SBA- 15, but none of these techniques have been able to yield a complete picture. PALS is a technique that has the potential to yield insight of the pore structure in SBA-15
Pp-Annihilation Into
No full text. The annihilation channels pp!! 0 , !j, !j 0 were studied with the Crystal Barrel detector at LEAR at p-momenta of 600, 1200, and 1940 MeV=c. In most cases angular distributions were measured which allowed a complete J P -analysis using the helicity formalism. The contribution of all relevant initial states could be determined. The maximal contributing angular momenta are dependent on the p-momentum and range up to J = 5. 1 Introduction This paper reports on the measurement of selected twobody pp-annihilation channels performed with the Crystal Barrel (CB) detector at LEAR at p-momenta of 600, 1200 and 1940 MeV=c. The aims of the measurements were 2-fold: (1) Determine the angular momenta in the pp-system, which contribute to the annihilation process with increasing p-momenta. This information is vital for the analysis of 3-or more body annihilation pro- ? This work is part of the PhD. thesis of K. Beuchert ?? Now at University of Freiburg, Freiburg,Germany ??? Universi..
Initial angular momentum state in pp annihilation at rest
No full textThe author shows that no quantitative statement on the relative importance of initial P-states in pp annihilation can be made. Annihilations in flight indicate that P-wave annihilation into K/sub 1 //sup 0/K/sub 1//sup 0/ is inhibited while annihilation into pi pi is enhanced and might suggest a P-wave contamination approximately 10%. The observatory of the final state K/sub 1//sup 0/K/sub 1//sup 0/n from annihilations at rest indicates that the depression of the K/sub 1//sup 0/K/sub 1//sup 0/ final state is not so important and suggests a P-wave contamination smaller than 4%. Furthermore the successes obtained in the analysis of various final states on the assumption of S-wave annihilation are hard to reconcile with a P-wave contribution bigger than approximately 5%. (20 refs)
Coupled Channel Analysis of the Pp-Annihilation Into
No full textThe three pseudoscalar meson final states of pp-annihilation at rest, 0 0 0 , 0 0 j and 0 jj have been studied together with scattering data. These channels have shown to be suitable to extract information on the I = 0 and I = 1 S- and D-waves. In particular the existence of two I G (J PC ) = 0 + (0 ++ ) resonances was reported in a previous analysis using a N/D inspired method. The aim of the analysis presented here is to quantify the compatibility of the data samples with respect to the resonance hypotheses of the applied partial waves. To apply consequently the K-matrix formalism for the production process within the Isobar model for the I = 0 S-wave a 3 \Theta 3 K-matrix had to be used. 1 Coupled channel analysis All three data samples, 0 0 0 , 0 0 j and 0 jj have been studied in the spirit of the Isobar model using the K--matrix formalism [1, 2, 3]. The final state interaction of pp-annihilation at rest into three mesons is considere..
Analysis of pp → ππ Data at Low Energy and its Implications
No full textThis thesis is a study of data on pp → ππ in the range 0.36 ≤ P(_lab) ≤ 1.55 GeV/c taken by the PS 172 experiment at CERN's LEAR facility. The aim is to elucidate the nature of mesonic states coupling both to baryon-antibaryon and meson-meson channels. The PS 172 data are compared with, and found to be consistent with, earlier data on the same channel, and, in a model independent way, the consistency of the PS 172 results with BNL data on pp pp → π(^0)π(^0) is also established. The first amplitude analysis of pp → π(^0)π(^0) to incorporate the PS 172 data is performed and it is found that from the hundreds of possible amplitudes, only two are compatible with the BNL pp → π(^0)π(^0) data and with threshold conditions. The latter may be applied in a far more rigorous way than has been previously possible since the PS 172 momentum range extends so close to threshold. Both of the solutions found exhibit resonances with spins 0-5 and the masses, widths and couplings of these states are deduced. The lowest spin resonances are found to have such large couplings to NN that they are unlikely to be simple qq states
Ga-doped ZnO films by magnetron sputtering at ultralow discharge voltages: Effects of defect annihilation
No full textPreparation of high quality transparent conductive oxide (TCO) films by sputter deposition involves an intricate balance of defect generation by the highly energetic negative oxygen ions (depending on the discharge voltage) and the concomitant annihilation of these defects during film growth. Ga-doped ZnO films with a low Ga content (1.7 at.%) were deposited to investigate the effects of defect annihilation on the microstructure evolutions as well as the optical and electrical properties. To achieve this aim, we prepared the GZO films by magnetron sputtering at ultralow discharge voltages (similar to 70 V) to minimize the defect generation, and varied the substrate temperature (from 130 degrees C to 380 degrees C) to adjust the annihilation rates. The microstructure was systematically characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Raman Spectroscopy. The electrical and optical properties were obtained by a Hall-effect measurement system and Spectroscopic Ellipsometry (SE), respectively. It was found that (i) even under the condition of highly controlled defect generation from the bombardment of negative oxygen ions, a sufficient annihilation of the defects cannot be realized without externally heating the substrate; and (ii) there existed a threshold temperature, above which both the structural quality and the electrical properties were improved with the increased temperature over the temperature range we examined. These results reveal that the growth temperature during the GZO film deposition has played an important role in effective annihilation of the irradiation-induced structural defects, which may be due to the higher diffusion barrier of Ga atoms in our GZO films. (C) 2017 Elsevier B.V. All rights reserved
Measurement of the b-hadron production cross section using decays to D∗ +μ −X final states in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV with the ATLAS detector
No full textThe b-hadron production cross section is measured with the ATLAS detector in pp collisions at
√<span style="text-decoration:overline">s</span>=7 TeV, using 3.3 pb−1
of integrated luminosity, collected during the 2010 LHC run. The b-hadrons
are selected by partially reconstructing D∗+μ
−X final states. Differential cross sections are measured as
functions of the transverse momentum and pseudorapidity. The measured production cross section for a
b-hadron withpT
>9 GeV and |η|<2.5 is 32.7±0.8(stat.)+4.5
−6.8
(syst.) µb, higher than the next-to-leadingorder QCD predictions but consistent within the experimental and theoretical uncertainties
Probing color coherence effects in pp collisions at √s = 7 TeV
No full textOpen Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the
source are credited. Funded by SCOAP3 / License Version CC BY 4.0.A study of color coherence effects in pp collisions at a center-of-mass energy of 7TeV is presented. The data used in the analysis were collected in 2010 with the CMS detector at the LHC and correspond to an integrated luminosity of 36 pb-1. Events are selected that contain at least three jets and where the two jets with the largest transverse momentum exhibit a back-to-back topology. The measured angular correlation between the second- and third-leading jet is shown to be sensitive to color coherence effects, and is compared to the predictions of Monte Carlo models with various implementations of color coherence. None of the models describe the data satisfactorily.BMWF and FWF (Austria); FNRS and FWO(Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil);MES
(Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF(Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland);
CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Republic of
Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, andUASLPFAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR(Russia);MESTD (Serbia); SEIDI and CPAN(Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA)
Measurement of ψ(2S) polarisation in pp collisions at √s = 7 TeV
No full textThe polarisation of prompt ψ(2S) mesons is measured by performing an angular analysis of ψ(2S) → μ+μ- decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum pT and rapidity y in the kinematic region 3.5 < pT < 15 GeV/c and 2.0 < y < 4.5, and is compared to theoretical models. No significant polarisation is observed
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