Study of

Tau lepton decays with open strangeness in the final state are measured with the OPAL detector at LEP to determine the strange hadronic spectral function of the tau lepton. The decays tau(-) -->(Kpi)(-)nu(tau)(Kpipipi)(-)nu(tau) and (Kpipipi)(-)nu(tau) with final states consisting of neutral and charged kaons and pions have been studied. The invariant mass distributions of 93.4% of these final states have been experimentally determined. Monte Carlo simulations have been used for the remaining 6.6% and for the strange final states including eta mesons. The reconstructed strange final states, corrected for resolution effects and detection efficiencies, yield the strange spectral function of the tau lepton. The moments of the spectral function and the ratio of strange to non-strange moments, which are important input parameters for theoretical analyses, are determined. Furthermore, the branching fractions B(tau(-) --> K(-)pi(o)nu(tau)) = (0.471 +/- 0.059(stat) +/- 0.023(sys))% and B(tau(-) --> K(-)pi(+)pi(-)nu(tau)) = (0.415 +/- 0.053(stat) +/- 0.040(sys))% have been measured.

The quenched chiral logs are examined on a $16^3 \times 28$ lattice with Iwasaki gauge action and overlap fermions. The pion decay constant $f_{\pi}$ is used to set the lattice spacing, $a = 0.200(3) {\rm fm}$. With pion mass as low as $\sim 180 {\rm MeV}$, we see the quenched chiral logs clearly in $m_{\pi}^2/m$ and $f_P$, the pseudoscalar decay constant. We analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory ($\chi$PT) to apply. With the constrained curve-fitting method, we are able to extract the quenched chiral log parameter $\delta$ together with other low-energy parameters. Only for $m_{\pi} \leq 300 {\rm MeV}$ do we obtain a consistent and stable fit with a constant $\delta$ which we determine to be 0.24(3)(4) (at the chiral scale $\Lambda_{\chi}=0.8 {\rm GeV}$). By comparing to the $12^3 \times 28$ lattice, we estimate the finite volume effect to be about 2.7% for the smallest pion mass. We also fitted the pion mass to the form for the re-summed cactus diagrams and found that its applicable region is extended farther than the range for the one-loop formula, perhaps up to $m_{\pi} \sim 500-600$ MeV. The scale independent $\delta$ is determined to be 0.20(3) in this case. We study the quenched non-analytic terms in the nucleon mass and find that the coefficient $C_{1/2}$ in the nucleon mass is consistent with the prediction of one-loop $\chi$PT\@. We also obtain the low energy constant $L_5$ from $f_{\pi}$. We conclude from this study that it is imperative to cover only the range of data with the pion mass less than $\sim 300 {\rm MeV}$ in order to examine the chiral behavior of the hadron masses and decay constants in quenched QCD and match them with quenched one-loop $\chi$PT\@.

We consider an inelastic dark matter model, where a fermion is charged under a broken U(1) gauge symmetry, and introduce a tiny Majorana mass term to split the fermion into two states with the light one being a dark matter candidate. If the gauge boson is light, it can mediate both elastic and inelastic dark matter self-interactions in dark halos, leading to observational consequences. Using a numerical technique based on partial wave analysis, we accurately calculate the elastic and inelastic self-scattering cross sections. We assume a thermal freeze-out scenario and fix the gauge coupling constant using the relic density constraint. Then, we focus on six benchmark masses of dark matter, covering a wide range from $10~{\rm MeV}$ to $160~{\rm GeV}$ and map parameter regions where the elastic scattering cross section per unit mass is within $1~{\rm cm^2/g} - 5~{\rm cm^2/g}$, favored to solve small-scale issues of cold dark matter. If the heavy state can decay to the light state and a massless species, the inelastic up-scattering process can cool the halo and lead to core collapse. Taking galaxies with evidence of dark matter density cores, we further derive constraints on the parameter space. For dark matter masses below $10~{\rm GeV}$, the mass splitting must be large enough to forbid up scattering in the dwarf halo for evading the core-collapse constraint; while for higher masses, the up-scattering process can still be allowed. Our results show astrophysical observations can provide powerful tests for dark matter models with large elastic and inelastic self-interactions.

We study the $J/\psi \to \phi \pi^+ a_0(980)^- (a_0^- \to \pi^- \eta)$ decay, showing that it delelops a triangle singularity at $M_{\rm inv}(\pi^+ a_0^-)$ around $1420 \, {\rm MeV}$. We evaluate the double mass distribution in terms of the $\pi^- \eta$ and $\pi^+ a^-_0$ invariant masses, observing that the $\pi^- \eta$ mass distribution exhibits the typical cusp structure of the $a_0(980)$ seen in recent high statistics experiments, and the $\pi^+ a^-_0$ spectrum shows clearly a peak around $M_{\rm inv}(\pi^+ a^-_0)=1420 \,{\rm MeV}$ which corresponds to a triangle singularity. By integrating over the two invariant masses, we predict a branching ratio for this decay of the order of $10^{-5}$, which is easily accessible in present laboratories. We also call the attention to the fact that the signal obtained is compatible with a bump experimentally observed in the $\eta \pi^+\pi^-$ mass distribution in the $J/\psi \to \phi \eta \pi^+\pi^-$ decay and encourage further analysis to extract from there the $\phi \pi^+ a_0^-$ and $\phi \pi^- a_0^+$ decay modes.

We investigate the relative importance of initial and final state effects on azimuthal correlations of gluons in low and high multiplicity p+Pb collisions. To achieve this, we couple Yang-Mills dynamics of pre-equilibrium gluon fields (IP-GLASMA) to a perturbative QCD based parton cascade for the final state evolution (BAMPS) on an event-by-event basis. We find that signatures of both the initial state correlations and final state interactions are seen in azimuthal correlation observables, such as $v_2\left\lbrace2PC\right\rbrace(p_T)$, their strength depending on the event multiplicity and transverse momentum. Initial state correlations dominate $v_2\left\lbrace2PC\right\rbrace(p_T)$ in low multiplicity events for transverse momenta $p_T>2~{\rm GeV}$. While final state interactions are dominant in high multiplicity events, initial state correlations affect $v_2\left\lbrace2PC\right\rbrace(p_T)$ for $p_T>2~{\rm GeV}$ as well as the pT integrated $v_2\left\lbrace2PC\right\rbrace$.

We use the Monte Carlo particle physics code FLUKA (Fluktuierende Kaskade) to calculate $\gamma$-ray spectra expected from solar flare energetic ion distributions. The FLUKA code includes robust physics-based models for electromagnetic, hadronic and nuclear interactions, sufficiently detailed for it to be a useful tool for calculating nuclear de-excitation, positron annihilation and neutron capture line fluxes and shapes, as well as $\approx \; {\rm GeV}$ continuum radiation from pion decay products. We show nuclear de-excitation $\gamma$-ray line model spectra from a range of assumed primary accelerated ion distributions and find them to be in good agreement with those found using the code of Murphy et al. (2009). We also show full $\gamma$-ray model spectra which exhibit all the typical structures of $\gamma$-ray spectra observed in solar flares. From these model spectra we build templates which are incorporated into the software package Objective Spectral Executive (OSPEX) and used to fit the combined Fermi Gamma-ray Burst Monitor (GBM)/Large Area Telescope (LAT) spectrum of the 2010 June 12 solar flare, providing a statistically acceptable result. To the best of our knowledge, the fit carried out with the FLUKA templates for the full $\gamma$-ray spectrum can be regarded as the first attempt to use a single code to implement a self-consistent treatment of the several spectral components in the photon energy range from $\approx 100$s ${\rm keV}$ to $\approx 100$s ${\rm MeV}$.

We have simulated QCD using 2+1 flavors of domain wall quarks on a $(2.74 {\rm fm})^3$ volume with an inverse lattice scale of $a^{-1} = 1.729(28)$ GeV. The up and down (light) quarks are degenerate in our calculations and we have used four values for the ratio of light quark masses to the strange (heavy) quark mass in our simulations: 0.217, 0.350, 0.617 and 0.884. We have measured pseudoscalar meson masses and decay constants, the kaon bag parameter $B_K$ and vector meson couplings. We have used SU(2) chiral perturbation theory, which assumes only the up and down quark masses are small, and SU(3) chiral perturbation theory to extrapolate to the physical values for the light quark masses. While next-to-leading order formulae from both approaches fit our data for light quarks, we find the higher order corrections for SU(3) very large, making such fits unreliable. We also find that SU(3) does not fit our data when the quark masses are near the physical strange quark mass. Thus, we rely on SU(2) chiral perturbation theory for accurate results. We use the masses of the $\Omega$ baryon, and the $\pi$ and $K$ mesons to set the lattice scale and determine the quark masses. We then find $f_\pi = 124.1(3.6)_{\rm stat}(6.9)_{\rm syst} {\rm MeV}$, $f_K = 149.6(3.6)_{\rm stat}(6.3)_{\rm syst} {\rm MeV}$ and $f_K/f_\pi = 1.205(0.018)_{\rm stat}(0.062)_{\rm syst}$. Using non-perturbative renormalization to relate lattice regularized quark masses to RI-MOM masses, and perturbation theory to relate these to $\bar{\rm MS}$ we find $ m_{ud}^{\bar{\rm MS}}(2 {\rm GeV}) = 3.72(0.16)_{\rm stat}(0.33)_{\rm ren}(0.18)_{\rm syst} {\rm MeV}$ and $m_{s}^{\bar{\rm MS}}(2 {\rm GeV}) = 107.3(4.4)_{\rm stat}(9.7)_{\rm ren}(4.9)_{\rm syst} {\rm MeV}$.

This document presents the searches for the flavour-changing neutral current decays B$0\atop{s}$ → μ+μ- and B$0\atop{s}$s → φμ+μ- . A data set with integrated luminosity of 300 pb-1 of proton-antiproton collisions at √ s = 1 . 96 TeV collected with the DØ detector in Run II of the FERMILAB Tevatron collider is used. The former decay mode is particularly sensitive to supersymmetric extensions of the Standard Model. For the latter mode, a measurement of the branching ratio could validate the prediction of the Standard Model. In the absence of an apparent signal, a limit on the branching fraction B(B$0\atop{s}$ → μ+μ-) can be computed by normalising the upper limit on the number of events in the B$0\atop{s}$ signal region to the number of reconstructed B ± → J/ψ K ± events. An upper limit on the branching fraction of B(B$0\atop{s}$ → μ+ μ- ) ≤ 3.7 × 10-7 at a 95% CL is obtained. This limit can be used to constrain models beyond the Standard Model. In models where the lightest supersymmetric particle is considered to be a dark matter candidate the limit aids in restricting the dark matter scattering cross section on nucleons. For the decay B$0\atop{s}$ → φμ+μ- also no signal has been observed and an upper limit on the branching ratio normalised to B$0\atop{s}$ → J/ψ φ events of B$0\atop{s}$ B(B$0\atop{s}$ → φ μ+ μ-)/B(B$0\atop{s}$→J/ψφ) < 4 . 4 × 10-3 at a 95% CL is obtained. In addition, the rare decay B$0\atop{s}$ → ψ (2 S ) φ has been observed. To measure a branching ratio, the B$0\atop{s}$ → J/ψ φ mode was used for normalisation, while B± → ψ (2S) K± and B± → J/ψ K± modes were used as control samples. The relative branching ratio has been measured to be B(B$0\atop{s}$ → ψ (2S) φ)/ B(B$0\atop{s}$ → J/ψ φ ) = 0 . 58 ± 0 . 24 (stat) ± 0 . 09 (sys).

An apparatus of the NBC type and the physics results obtained

A nonbubble chamber (NBC) setup, especially designed to perform a series of experiments, is described. The setup consists of a neutron missing-mass spectrometer coupled with a system of large electromagnetic shower detectors. In spite of its large dimensions (the sensitive surface and volume are 2.16 × 104 cm2 and 7.8 × 105 cm3, respectively), the neutron spectrometer has a time resolution of ±0.70 nsec FWHM, with ∼25% detection efficiency in the range (70–390 MeV) neutron kinetic energy. The time equalization between the various components of the neutron spectrometer has been established to within ±0.1 nsec. At present this is the most powerful and the most accurate high-energy neutron detector. The electromagnetic shower detector is based on the principle of simultaneous measurements of the spatial development of the electromagnetic cascade and of its energy release. This is obtained with nine elements of lead foil — spark chamber — plastic scintillator, all sandwiched together. The sensitive surface and volume of the electromagnetic shower detector are 1.45 × 104 cm2 and 7.2 × 105 cm3, respectively. The setup has been used to perform a series of 14 experimental investigations. Ten of these have already produced conclusive results which are either published or submitted for publication: 1. 1. Evidence against the existence of the S0 meson; 2. 2. an accurate measurement of the branching ratio η → neutrals η → total ; 3. 3. an accurate determination of the branching ratio ω → neutrals ω → total ; 4. 4. study of φ production in π− + p interactions at 2.1 GeV/c; 5. 5. evidence for the new decay mode φ → e+e− and measurement of the cross section σ[π− + p → (φ → e+e−) + n]; 6. 6. evidence for the new decay mode ω → e+e− and measurement of the cross section σ[π− + p → (ω → e+e−) + n]; 7. 7. points (5) and (6) above allowed the first direct determination of the (ω − φ) mixing angle; 8. 8. evidence for the new decay mode X0 → γγ; 9. 9. cross section measurements for X0 production and value of the branching ratio X 0 → neutrals X 0 → total ; 10. 10. evidence for a structure in the neutral A2 mass region. The data of the following three experiments are being analysed: 11. 11. measurement of the branching ratio X 0 → γγ X 0 → total ; 12. 12. study of the ϱ − ω interference in the reaction π− + p → π+ + π− + n at 1.67GeV/c incident pion momentum; 13. 13. study of the (π0π0) system in the invariant mass region from 400–950 MeV. 14. 14. Finally, the last experiment is still under way: the apparatus is at present running for the detection of the decay mode φ → η + γ and for the measurement of the branching ratio φ → η + γ φ → total . The setup described and the experimental results obtained show that it is possible, in the field of NBC physics, to reduce the cost and the time needed for an experiment provided that multipurpose NBC setups are used.

The recent limits, $$m_{\tilde g} , m_{\tilde q} \gtrsim 40$$ , GeV for gluino and squark masses obtained from experiments at the collider are based on jet +p T analysis, in the hypothesis that the gluino or the squark decays into photino+quarks with a branching ratio near to one. We show that this hypothesis is generally not justified for higher masses of the gluino and the squarks, 50 GeV $$ \lesssim m_{\tilde g,\tilde q} \lesssim $$ 150 GeV, relevant to present and future $$\bar p$$ colliders. In an interesting range of the parameters we study the different decay modes and the related signatures, among which isolated leptons or photons in the final states.

We report a search for $B$ decays to selected final states with the $\eta_c$ meson: $B^{\pm}\to K^{\pm}\eta_c\pi^+\pi^-$, $B^{\pm}\to K^{\pm}\eta_c\omega$, $B^{\pm}\to K^{\pm}\eta_c\eta$ and $B^{\pm}\to K^{\pm}\eta_c\pi^0$. The analysis is based on $772\times 10^6$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We set 90\% confidence level upper limits on the branching fractions of the studied $B$ decay modes, independent of intermediate resonances, in the range $(0.6-5.3)\times 10^{-4}$. We also search for molecular-state candidates in the $D^0\bar{D}^{*0}-\bar{D}^0D^{*0}$, $D^0\bar{D}^0+\bar{D}^0D^0$ and $D^{*0}\bar{D}^{*0}+\bar{D}^{*0}D^{*0}$ combinations, neutral partners of the $Z(3900)^{\pm}$ and $Z(4020)^{\pm}$, and a poorly understood state $X(3915)$ as possible intermediate states in the decay chain, and set 90\% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range $(0.6-6.9)\times 10^{-5}$.

The spectral functions of the vector current and the axial-vector current have been measured in hadronic $\tau$ decays using the OPAL detector at LEP. Within the framework of the Operator Product Expansion a simultaneous determination of the strong coupling constant $\alpha_{\rm s}$ , the non-perturbative operators of dimension 6 and 8 and of the gluon condensate has been performed. Different perturbative descriptions have been compared to the data. The Contour Improved Fixed Order Perturbation Theory gives $\alpha_{\rm s}(m_\tau^2) = 0.348 \pm 0.009_{\rm exp} \pm 0.019_{\rm theo}$ at the $\tau$ -mass scale and $\alpha_{\rm s}(m^2_{\rm Z}) = 0.1219 \pm 0.0010_{\rm exp} \pm 0.0017_{\rm theo}$ at the ${\rm Z}^0$ -mass scale. The values obtained for $\alpha_{\rm s}(m^2_{\rm Z})$ using Fixed Order Perturbation Theory or Renormalon Chain Resummation are 2.3% and 4.1% smaller, respectively. The ‘running’ of the strong coupling between $s_0 \simeq 1.3 {\rm GeV}^2$ and $s_0 = m_\tau^2$ has been tested from direct fits to the integrated differential hadronic decay rate $R_\tau(s_0)$ . A test of the saturation of QCD sum rules at the $\tau$ -mass scale has been performed.

A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy \ee annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between \ee and $\tau$ spectral functions in the $\pi\pi$ channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and $1.0 {\rm GeV}/c^2$.The deviations from the measurement at BNL are found to be $(22.1 \pm 7.2 \pm 3.5 \pm 8.0)~10^{-10}$ (1.9 $\sigma$) and $(7.4 \pm 5.8 \pm 3.5 \pm 8.0)~10^{-10}$ (0.7 $\sigma$) for the \ee- and $\tau$-based estimates, respectively, where the second error is from the nonhadronic contributions and the third one from the BNL measurement. Taking into account the $\rho^- - \rho^0$ mass splitting determined from the measured spectral functions increases the $\tau$-based estimate and leads to a worse discrepancy between the two estimates.

We carry out a systematic study of branching ratios, angular correlations, and $\mathrm{CP}$ asymmetries in the decay of neutral and charged $B$ mesons to final states consisting of two vector mesons. The renormalization-group-improved effective Hamiltonian is evaluated in the vacuum insertion (factorization) approximation. Okubo-Zweig-Iizuka suppressed and annihilation terms are neglected. Current matrix elements are evaluated using the wave functions of Bauer, Stech, and Wirbel. Branching ratios and angular correlations among subsequent decays of the vector mesons are calculated for 34 channels and a comparison is made with the data. As a first approximation, the calculational scheme provides a useful framework with which to organize the data. Interesting direct $\mathrm{CP}$ asymmetries are particularly evident in ${K}^{*}\ensuremath{\omega}$ and ${K}^{*}\ensuremath{\rho}$ final states, where branching ratios are moderate. They are excellent probes of penguin term influence on decay amplitudes. Even larger direct asymmetries are present in $\ensuremath{\omega}\ensuremath{\rho}$ and $\ensuremath{\rho}\ensuremath{\rho}$ final states where, however, branching ratios are low and results are very model dependent. We show how ${B}^{0}\ensuremath{-}{\overline{B}}^{0}$ mixing phases are influenced by phases in the direct amplitudes. The effect is particularly strong for ${\overline{K}}^{*0}{\overline{D}}^{*0}$ final states.