208868428
f1(1285) formation in two-photon collisions at LEP
Abstract The ηπ + π − final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb −1 . The f 1 (1285) meson is observed and the Q 2 dependence of its production is compared to different form factor models. The γγ -coupling parameter Γ γγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ (f 1 (1285)→a 0 π )/ Γ (f 1 (1285)→ ηππ ) is also measured.
116857589
Inclusive $\pi^0$ and $K^0_{S}$ production in two photon collisions at LEP
The reactions e + e − →e + e − π 0 X and e + e − →e + e − K S 0 X are studied using data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 202 GeV. Inclusive differential cross sections are measured as a function of the particle transverse momentum p t and the pseudo-rapidity. For p t ⩽1.5 GeV, the π 0 and K S 0 differential cross sections are described by an exponential, typical of soft hadronic processes. For p t ⩾1.5 GeV, the cross sections show the presence of perturbative QCD processes, described by a power-law. The data are compared to Monte Carlo predictions and to NLO QCD calculations.
120107147
Partial wave analysis of psi-prime ---> pi+ pi- pi0 at BESII
11446512
The ONSEN Data Reduction System for the Belle II Pixel Detector
We present an FPGA-based online data reduction system for the pixel detector of the future Belle II experiment. The occupancy of the pixel detector is estimated at 3%. This corresponds to a data output rate of more than 20 GB/s after zero suppression, dominated by background. The Online Selection Nodes (ONSEN) system aims to reduce the background data by a factor of 30. It consists of 33 MicroTCA cards, each equipped with a Xilinx Virtex-5 FPGA and 4 GiB DDR2 RAM. These cards are hosted by 9 AdvancedTCA carrier boards. The ONSEN system buffers the entire output data from the pixel detector for up to 5 seconds. During this time, the Belle II high-level trigger PC farm performs an online event reconstruction, using data from the other Belle II subdetectors. It extrapolates reconstructed tracks to the layers of the pixel detector and defines regions of interest around the intercepts. Based on this information, the ONSEN system discards all pixels not inside a region of interest before sending the remaining hits to the event builder system. During a beam test with one layer of the pixel detector and four layers of the surrounding silicon strip detector, including a scaled-down version of the high-level trigger and data acquisition system, the pixel data reduction using regions of interest was exercised. We investigated the data produced in more than 20 million events and verified that the ONSEN system behaved correctly, forwarding all pixels inside regions of interest and discarding the rest.
120497934
Measurement of the cross section for open-beauty production in photon–photon collisions at LEP
Abstract The cross section for open-beauty production in photon–photon collisions is measured using the whole high-energy and high-luminosity data sample collected by the L3 detector at LEP. This corresponds to 627 pb −1 of integrated luminosity for electron–positron centre-of-mass energies from 189 to 209 GeV. Events containing b quarks are identified through their semi-leptonic decay into electrons or muons. The e + e − → e + e − b b ¯ X cross section is measured within our fiducial volume and then extrapolated to the full phase space. These results are found to be in significant excess with respect to Monte Carlo predictions and next-to-leading order QCD calculations.
125927421
Measurement of the mass of the tau lepton.
Author(s): Bai, JZ; Bardon, O; Becker-Szendy, RA; Blum, I; Breakstone, A; Burnett, T; Chen, GP; Chen, HF | Abstract: A data-driven energy scan in the immediate vicinity of the τ pair production threshold has been performed using the Beijing Spectrometer at the Beijing Electron-Positron Collider. Approximately 5pb-1of data, distributed over 12 scan points, have been collected. A previous mass value for the τ lepton, obtained using only the eµ final state, has been published. In this paper, the final BES result on the mass measurement is presented. The analysis is based on the combined data from the ee, eµ, eh, µµ, µh, and hh final states, where h denotes a charged Π or K. A maximum likelihood fit to the τ pair production cross section data yields the value mT=1776.96-0.21-0.17+0.18+0.25. © 1995 The American Physical Society.
118355581
Diquark effects in light baryon correlators from lattice QCD
We study the role of diquarks in light baryons through point-to-point baryon correlators. We contrast results from quenched simulations with ones with two flavors of dynamical overlap fermions. The scalar, pseudoscalar, and axial vector diquarks are combined with light quarks to form color singlets. The quenched simulation shows large zero-mode effects in correlators containing the scalar and pseudoscalar diquark. The two scalar diquarks created by {gamma}{sub 5} and {gamma}{sub 0}{gamma}{sub 5} lead to different behavior in baryon correlators, showing that the interaction of diquarks with the third light quark matters: we do not see an isolated diquark. In our quark mass range, the scalar diquark created by {gamma}{sub 5} seems to play a greater role than the others.
119220539
Potential precision of a direct measurement of the Higgs boson total width at a muon collider
In the light of the discovery of a 126 GeV Standard-Model-like Higgs boson at the LHC, we evaluate the achievable accuracies for direct measurements of the width, mass, and the $s$-channel resonant production cross section of the Higgs boson at a proposed muon collider. We find that with a beam energy resolution of $R=0.01%$ (0.003%) and integrated luminosity of $0.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ ($1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$), a muon collider would enable us to determine the Standard-Model-like Higgs width to $\ifmmode\pm\else\textpm\fi{}0.35\text{ }\text{ }\mathrm{MeV}$ ($\ifmmode\pm\else\textpm\fi{}0.15\text{ }\text{ }\mathrm{MeV}$) by combining two complementary channels of the $W{W}^{*}$ and $b\overline{b}$ final states. A non-Standard-Model Higgs with a broader width is also studied. The unparalleled accuracy potentially attainable at a muon collider would test the Higgs interactions to a high precision.
119279570
Dark matter and Higgs bosons in the MSSM
A bstractWe investigate dark matter (DM) in the context of the minimal supersymmetric extension of the standard model (MSSM). We scan through the MSSM parameter space and search for solutions that (a) are consistent with the Higgs discovery and other collider searches; (b) satisfy the flavor constraints from B physics; (c) give a DM candidate with the correct thermal relic density; and (d) are allowed by the DM direct detection experiments. For the surviving models with our parameter scan, we find the following features: (1) The DM candidate is largely a Bino-like neutralino with non-zero but less than 20% Wino and Higgsino fractions; (2) The relic density requirement clearly pins down the solutions from the Z and Higgs resonances (Z, h, H, A funnels) and co-annihilations; (3) Future direct search experiments will likely fully cover the Z, h funnel regions, and H, A funnel regions as well except for the “blind spots”; (4) Future indirect search experiments will be more sensitive to the CP-odd Higgs exchange due to its s-wave nature; (5) The branching fraction for the SM-like Higgs decay to DM can be as high as 10%, while those from heavier Higgs decays to neutralinos and charginos can be as high as 20%. We show that collider searches provide valuable information complementary to what may be obtained from direct detections and astroparticle observations. In particular, the Z- and h-funnels with a predicted low LSP mass should be accessible at future colliders. Overall, the Higgs bosons may play an essential role as the portal to the dark sector.
118545965
Low-mass Higgs bosons in the NMSSM and their LHC implications
A bstractWe study the Higgs sector of the Next to Minimal Supersymmetric Standard Model (NMSSM) in light of the discovery of the SM-like Higgs boson at the LHC. We perform a broad scan over the NMSSM parameter space and identify the regions that are consistent with current Higgs search results at colliders. In contrast to the commonly studied “decoupling” scenario in the literature where the Minimal Supersymmetric Standard Model CP-odd Higgs boson mass is large mA ≫ mZ , we pay particular attention to the light Higgs states in the case when mA ≲ 2mZ . The Higgs bosons in the NMSSM, namely three CP-even states, two CP-odd states, and two charged Higgs states, could all be rather light, near or below the electroweak scale, although the singlet-like states can be heavier. The SM-like Higgs boson could be either the lightest CP-even scalar or the second lightest CP-even scalar, but is unlikely to be the heaviest scalar. These NMSSM parameter regions have unique properties and offer rich phenomenology. The decay branching fractions for the SM-like Higgs boson may be modified appreciably. The correlations of γγ/V V and $ {VV \left/ {{b\overline{b}}} \right.} $ can be substantially altered. The new Higgs bosons may be readily produced at the LHC and may decay to non-standard distinctive final states, most notably a pair of Higgs bosons when kinematically accessible. We evaluate the production and decay of the Higgs bosons and comment on further searches at the LHC to probe the Higgs sector of the NMSSM.
85538672
Study of kaon decay to two pions
The weak decay of the kaon to two pions is studied within the model of Nambu and Jona-Lasinio. Using the standard effectiveweak Hamiltonian, both the decay amplitude arising from an intermediate state σ meson and the direct decay amplitude are calculated. The effect of final state interactions is also included. When the matching scale is chosen such that the decay amplitude with isospin I ¼ 2 is close to its experimental value, our model including the σ meson contributes up to 80% of the total I ¼ 0 amplitude. This supports recent suggestions that the σ meson should play a vital role in explaining the ΔI ¼ 1=2 rule in this system.