106 research outputs found

    Strong and Weak Phases from Time-Dependent Measurements of BππB \to \pi \pi

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    Time-dependence in B0(t)π+πB^0(t) \to \pi^+ \pi^- and \ob(t) \to \pi^+ \pi^- is utilized to obtain a maximal set of information on strong and weak phases. One can thereby check theoretical predictions of a small strong phase δ\delta between penguin and tree amplitudes. A discrete ambiguity between δ0\delta \simeq 0 and δπ\delta \simeq \pi may be resolved by comparing the observed charge-averaged branching ratio predicted for the tree amplitude alone, using measurements of BπlνB \to \pi l \nu and factorization, or by direct comparison of parameters of the Cabibbo-Kobayashi-Maskawa (CKM) matrix with those determined by other means. It is found that with 150 fb1^{-1} from BaBar and Belle, this ambiguity will be resolvable if no direct CP violation is found. In the presence of direct CP violation, the discrete ambiguity between δ\delta and πδ\pi - \delta becomes less important, vanishing altogether as δπ/2|\delta| \to \pi/2. The role of measurements involving the lifetime difference between neutral BB eigenstates is mentioned briefly.Comment: 14 pages, LaTeX, 5 figures, to be published in Phys. Rev. D. Updated version with one reference change

    Precise calculation of parity nonconservation in cesium and test of the standard model

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    We have calculated the 6s-7s parity nonconserving (PNC) E1 transition amplitude, E_{PNC}, in cesium. We have used an improved all-order technique in the calculation of the correlations and have included all significant contributions to E_{PNC}. Our final value E_{PNC} = 0.904 (1 +/- 0.5 %) \times 10^{-11}iea_{B}(-Q_{W}/N) has half the uncertainty claimed in old calculations used for the interpretation of Cs PNC experiments. The resulting nuclear weak charge Q_{W} for Cs deviates by about 2 standard deviations from the value predicted by the standard model.Comment: 24 pages, 8 figure

    Two-loop scalar self-energies in a general renormalizable theory at leading order in gauge couplings

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    I present results for the two-loop self-energy functions for scalars in a general renormalizable field theory, using mass-independent renormalization schemes based on dimensional regularization and dimensional reduction. The results are given in terms of a minimal set of loop-integral basis functions, which are readily evaluated numerically by computers. This paper contains the contributions corresponding to the Feynman diagrams with zero or one vector propagator lines. These are the ones needed to obtain the pole masses of the neutral and charged Higgs scalar bosons in supersymmetry, neglecting only the purely electroweak parts at two-loop order. A subsequent paper will present the results for the remaining diagrams, which involve two or more vector lines.Comment: 26 pages, 4 figures, revtex4, axodraw.sty. Version 2: sentence after eq. (A.13) corrected, references added. Version 3: typos in eqs. (5.17), (5.20), (5.21), (5.32) are corrected. Also, the MSbar versions of eqs. (5.32) and (5.33) are now include

    Study of KS KL Coupled Decays and KL -Be Interactions with the CMD-2 Detector at VEPP-2M Collider

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    The integrated luminosity about 4000 inverse nanobarn of around phi meson mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30 % of available data is presented in this paper. The KS KL pairs from phi meson decays were reconstructed in the drift chamber when both kaons decayed into two charged particles. From a sample of 1423 coupled decays a selection of candidates to the CP violating KL into pi+ pi- decay was performed. CP violating decays were not identified because of the domination of events with a KL regenerating at the Be beam pipe into KS and a background from KL semileptonic decays. The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +- 17 mb in agreement with theoretical expectations. The angular distribution of KS mesons after regeneration and the total cross section of KL for Be have been measured.Comment: 14 pages, 8 figure

    The Isgur-Wise function in a relativistic model for qQˉq\bar Q system

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    We use the Dirac equation with a ``(asymptotically free) Coulomb + (Lorentz scalar) linear '' potential to estimate the light quark wavefunction for qQˉ q\bar Q mesons in the limit mQm_Q\to \infty. We use these wavefunctions to calculate the Isgur-Wise function ξ(v.v)\xi (v.v^\prime ) for orbital and radial ground states in the phenomenologically interesting range 1v.v41\leq v.v^ \prime \leq 4. We find a simple expression for the zero-recoil slope, ξ(1)=1/2ϵ2/3\xi^ \prime (1) =-1/2- \epsilon^2 /3, where ϵ\epsilon is the energy eigenvalue of the light quark, which can be identified with the Λˉ\bar\Lambda parameter of the Heavy Quark Effective Theory. This result implies an upper bound of 1/2-1/2 for the slope ξ(1)\xi^\prime (1). Also, because for a very light quark q(q=u,d)q (q=u, d) the size \sqrt {} of the meson is determined mainly by the ``confining'' term in the potential (γσr)(\gamma_\circ \sigma r), the shape of ξu,d(v.v)\xi_{u,d}(v.v^\prime ) is seen to be mostly sensitive to the dimensionless ratio Λˉu,d2/σ\bar \Lambda_{u,d}^2/\sigma. We present results for the ranges of parameters 150MeV<Λˉu,d<600MeV150 MeV <\bar \Lambda_{u,d} <600 MeV (ΛˉsΛˉu,d+100MeV)(\bar\Lambda_s \approx \bar\Lambda_{u,d}+100 MeV), 0.14GeV2σ0.25GeV20.14 {GeV}^2 \leq \sigma \leq 0.25 {GeV}^2 and light quark masses mu,md0,ms=175MeVm_u, m_d \approx 0, m_s=175 MeV and compare to existing experimental data and other theoretical estimates. Fits to the data give: Λˉu,d2/σ=4.8±1.7{\bar\Lambda_{u,d}}^2/\sigma =4.8\pm 1.7 , ξu,d(1)=2.4±0.7-\xi^\prime_{u,d}(1)=2.4\pm 0.7 and VcbτB1.48ps=0.050±0.008\vert V_{cb} \vert \sqrt {\frac {\tau_B}{1.48 ps}}=0.050\pm 0.008 [ARGUS '93]; Λˉu,d2/σ=3.4±1.8{\bar\Lambda_{u,d}}^2/\sigma = 3.4\pm 1.8, ξu,d(1)=1.8±0.7-\xi^\prime_{u,d}(1)=1.8\pm 0.7 and VcbτB1.48ps=0.043±0.008\vert V_{cb} \vert \sqrt { \frac {\tau_B}{1.48 ps}}=0.043\pm 0.008 [CLEO '93]; ${\bar\Lambda_{u,d}}^2/Comment: 22 pages, Latex, 4 figures (not included) available by fax or via email upon reques

    Coherent Photoproduction of pi^+ from 3^He

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    We have measured the differential cross section for the γ\gamma3^3Heπ+t\rightarrow \pi^+ t reaction. This reaction was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid 3^3He target. The differential cross sections for the γ\gamma3^3Heπ+t\rightarrow \pi^+ t reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.Comment: 11 pages, 16 figure

    eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV

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    Differential cross sections for the reaction gamma p -> eta-prime p have been measured with the CLAS spectrometer and a tagged photon beam with energies from 1.527 to 2.227 GeV. The results reported here possess much greater accuracy than previous measurements. Analyses of these data indicate for the first time the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710) resonances, known to couple strongly to the eta N channel in photoproduction on the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure

    A Bayesian analysis of pentaquark signals from CLAS data

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    We examine the results of two measurements by the CLAS collaboration, one of which claimed evidence for a Θ+\Theta^{+} pentaquark, whilst the other found no such evidence. The unique feature of these two experiments was that they were performed with the same experimental setup. Using a Bayesian analysis we find that the results of the two experiments are in fact compatible with each other, but that the first measurement did not contain sufficient information to determine unambiguously the existence of a Θ+\Theta^{+}. Further, we suggest a means by which the existence of a new candidate particle can be tested in a rigorous manner.Comment: 5 pages, 3 figure

    Measurement of the Deuteron Structure Function F2 in the Resonance Region and Evaluation of Its Moments

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    Inclusive electron scattering off the deuteron has been measured to extract the deuteron structure function F2 with the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The measurement covers the entire resonance region from the quasi-elastic peak up to the invariant mass of the final-state hadronic system W~2.7 GeV with four-momentum transfers Q2 from 0.4 to 6 (GeV/c)^2. These data are complementary to previous measurements of the proton structure function F2 and cover a similar two-dimensional region of Q2 and Bjorken variable x. Determination of the deuteron F2 over a large x interval including the quasi-elastic peak as a function of Q2, together with the other world data, permit a direct evaluation of the structure function moments for the first time. By fitting the Q2 evolution of these moments with an OPE-based twist expansion we have obtained a separation of the leading twist and higher twist terms. The observed Q2 behaviour of the higher twist contribution suggests a partial cancellation of different higher twists entering into the expansion with opposite signs. This cancellation, found also in the proton moments, is a manifestation of the "duality" phenomenon in the F2 structure function

    Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24

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    Recently, using Greenwich and Solar Optical Observing Network sunspot group data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I), has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg latitude interval of the Sun's northern hemisphere and in the time-interval of -1.35 year to +2.15 year from the time of the preceding minimum of a solar cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the areas of the spot groups in 0-10 deg latitude interval of the southern hemisphere and in the time-interval of 1.0 year to 1.75 year just after the time of the maximum of the cycle n correlates very well (r=0.966) with the amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or - 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude of the upcoming cycle 24. Here we found that in case of (1), the north-south asymmetry in the area sum of a cycle n also has a relationship, say (3), with the amplitude of cycle n+1, which is similar to (1) but more statistically significant (r=0.968) like (2). By using (3) it is possible to predict the amplitude of a cycle with a better accuracy by about 13 years in advance, and we get 103 + or -10 for the amplitude of the upcoming cycle 24. However, we found a similar but a more statistically significant (r=0.983) relationship, say (4), by using the sum of the area sum used in (2) and the north-south difference used in (3). By using (4) it is possible to predict the amplitude of a cycle by about 9 years in advance with a high accuracy and we get 87 + or - 7 for the amplitude of cycle 24.Comment: 21 pages, 7 figures, Published in Solar Physics 252, 419-439 (2008
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