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At least 109 records · Page 6Linked to original sources
arXiv2007

Theoretical progress on the V_us determination from tau decays

A very precise determination of V_us can be obtained from the semi-inclusive hadronic decay width of the tau lepton into final states with strangeness. The ratio of the Cabibbo-suppressed and Cabibbo-allowed tau decay widths directly measures (V_us/V_ud)^2, up to very small SU(3)-breaking corrections which can be theoretically estimated with the needed accuracy. Together with previous LEP and CLEO data, the recent measurements by Babar and Belle of some Cabibbo-suppressed tau decays imply V_us= 0.2165 +- 0.0026_exp +- 0.0005_th, which is already competitive with the standard extraction from K_l3 decays. The uncertainty is largely dominated by experimental errors and should be easily reduced with the high statistics of the B factories, providing the most accurate determination of this parameter. A 1% experimental precision on the Cabibbo-suppressed tau decay width would translate into a 0.6% uncertainty on V_us.

hep-ph↗
arXiv2007

The total cross section at the LHC

We do not have the ability to perform precise calculations of long-range strong interaction effects, because the effective QCD coupling is not small and so we cannot use perturbation theory. Nevertheless, I show that we know a lot, though not nearly enough. As a measure of our lack of knowledge, the best prediction for the total cross section at LHC energy is 125 +/- 25 mb.

hep-ph↗
arXiv2007

SuperB: A High-Luminosity Asymmetric e+ e- Super Flavor Factory. Conceptual Design Report

The physics objectives of SuperB, an asymmetric electron-positron collider with a luminosity above 10^36/cm^2/s are described, together with the conceptual design of a novel low emittance design that achieves this performance with wallplug power comparable to that of the current B Factories, and an upgraded detector capable of doing the physics in the SuperB environment.

hep-ex↗
arXiv2007

Searches for New Physics by the H1 Experiment at HERA

The high energy program of the HERA $ep$ collider ended in March 2007, where data equivalent to an integrated luminosity of $\sim$ 0.5 fb$^{-1}$ has been collected by the H1 experiment. In this context, some of the most recent results from H1 about searches for new phenomena are presented.

hep-ex↗
arXiv2007

Model-independent WIMP Searches at the ILC

We investigate the possibility to detect WIMPs at the ILC in a model-independent way using events with single photons. The study is done with a full detector simulation of the LDC detector and MarlinReco. It turns out that WIMPs are observable this way at the ILC if their coupling to electrons is not too small. Beam polarisation can increase the accessible phase space significantly.

hep-ex↗
arXiv2007

The Neutron EDM Experiment

The neutron EDM experiment has played an important part over many decades in shaping and constraining numerous models of CP violation. This review article discusses some of the techniques used to calculate EDMs under various theoretical scenarios, and highlights some of the implications of EDM limits upon such models. A pedagogical introduction is given to the experimental techniques employed in the recently completed ILL experiment, including a brief discussion of the dominant systematic uncertainties. A new and much more sensitive version of the experiment, which is currently under development, is also outlined.

hep-ex↗
arXiv2007

Recent results on 4-body, charm semileptonic decays

We summarize recent data on 4-body charm semileptonic decay concentrating on \kklndk{} and \kpilndk{}. We begin with giving some motivation for the study of these decays. We discuss several of the models traditionally used to describe these decays and conclude by presenting a non-parametric analysis of \kpiendk{} and its possible extension into non-parametric studies of \kpimndk{}.

hep-ex↗
arXiv2007

Did one observe couplings of right-handed quarks to W ?

I consider non standard EW couplings of light right-handed quarks to W and Z suggested in a systematic non decoupling bottom-up low-energy effective theory approach to possible extensions of the Standard Model. New experimental tests in K^L_{mu3} decays based on recent measurements and scalar form factor analysis are discussed. A successful NLO fit to the standard set of Z-pole and other NC data is presented as well.

hep-ph↗
arXiv2007

Branching Fractions and Direct CP Asymmetries of Charmless B Decay Modes at CDF

We present new CDF results on the branching fractions and time-integrated direct CP asymmetries for $B^0$ and $B^0_s$ decay modes into pairs of charmless charged hadrons (pions or kaons). The data-set for this update amounts to 1 $\mathrm{fb}^{-1}$ of $p\bar p$ collisions at a center of mass energy 1.96 $\mathrm{TeV}$. We report the first observation of the $B_s \to K^- π^+$ mode and a measurement of its branching fraction and direct CP asymmetry. We also observe for the first time two charmless decays of the $Λ_b^0$-baryon: $Λ_b^0 \to pπ^-$ and $Λ_b^0 \to pK^-$.

hep-ex↗
arXiv2008

Charm

New results on properties and decays of open charm and charmonium states are reviewed. The emphasis is on examples that illustrate the various aspects through which studies of charm physics impact the field.

hep-ex↗
arXiv2007

K-matrix and Dalitz plot analysis from FOCUS

Dalitz analysis is a powerful tool for physics studies within and beyond the Standard Model. In the last decade it has helped to investigate the Heavy Flavor hadronic decay dynamics and is now being applied to extract angles of the CKM Unitarity triangle. To perform such sophisticate analyses we need to model the strong interaction effects. The FOCUS experiment has performed pilot studies in the charm sector through the K-matrix formalism. What has been learnt from charm will be beneficial for future accurate beauty measurements. Experience and results from FOCUS are presented and discussed.

hep-ex↗
arXiv2007

Charm-Production in e^+e^- Annihilation Around 4 GeV

Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of $D^+$, $D^0$ and $D_s^+$ mesons in $e^{+}e^{-}$ annihilations at thirteen center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charmed mesons ($D\bar{D}$, $D^{*}\bar{D}$, $D^{*}\bar{D}^{*}$, $D_s^+ D_s^-$, $D_s^{*+} D_s^-$, and $D_s^{*+} D_s^{*-}$) and for processes in which the charmed meson pair is accompanied by a pion.

hep-ex↗
arXiv2007

Searches for Leptoquark Production at D0

Recent searches for leptoquark production in proton-antiproton collisions at sqrt(s)=1.96TeV are presented using data samples with integrated luminosities up to 1fb^(-1) recorded with the D0 detector.

hep-ex↗
arXiv2007

QCD symmetries in excited hadrons

Recent developments for chiral and $U(1)_A$ restorations in excited hadrons are reviewed. We emphasize predictions of the chiral symmetry restoration scenario for axial charges and couplings to Goldstone bosons. Using very general chiral symmetry arguments it is shown that strict chiral restoration in a given excited nucleon forbids its decay into the $N π$ channel. We confront this prediction with the $N^*Nπ$ coupling constants extracted from the decay widths and observe a 100 % correlation of these data with the spectroscopic parity doublet patterns. These results suggest that the lowest approximate chiral parity doublet is the $N(1440) - N(1535)$ pair. In the meson sector we discuss predictions of the chiral symmetry restoration for still missing states and a signature of the higher symmetry observed in new $\bar p p$ data. We conclude with the exactly solvable chirally symmetric and confining model that can be considered as a generalization of the 1+1 dimensional 't Hooft model to 4 dimensions. Complete spectra of $\bar q q$ mesons demonstrate a fast chiral restoration with increasing $J$ and a slow one with increasing $n$.

hep-ph↗
arXiv2007

Study of the Exclusive Initial-State-Radiation Production of the DDbar System

A search for charmonium and other new states is performed in a study of exclusive initial-state-radiation production of D Dbar events from electron-positron annihilations at a center-of-mass energy of 10.58 GeV. The data sample corresponds to an integrated luminosity of 384 fb-1 and was recorded by the BABAR experiment at the PEP-II storage ring. The D Dbar mass spectrum shows clear evidence of the psi(3770) plus other structures near 3.9, 4.1, and 4.4 GeV/c^2. No evidence for Y(4260) -> D Dbar is observed, leading to an upper limit of B(Y(4260) -> D Dbar)/B(Y(4260) -> J/psi pi+ pi-) < 1.0 at 90 % confidence level.

hep-ex↗
arXiv2007

Charmless b-hadron decays at CDF

I present recent results of measurements of branching fractions and CP-violating asymmetries in B0, Bs, and Lambda_B two-body charmless decays at the upgraded Collider Detector at the Fermilab Tevatron. Measurements of rates of flavor-changing neutral current B0, Bs -->mu+mu- and B+/B0/Bs --> mu+mu- K+/K*0/phi decays are also reported. The results are extracted from samples corresponding to time-intergrated luminosities ranging from 0.78 to 1 fb-1.

hep-ex↗
arXiv2007

Lifetime Difference and CP Asymmetry in the Bs -> J/psi phi decay

The Bs meson is an interesting particle to study because a sizable mixing induced CP violation in the Bs-Bsbar system would be an indication for physics beyond the Standard Model. In this paper we present a measurement of the lifetime difference DeltaGamma between the Bs mass eigenstates and the CP violating phase in the decay Bs -> J/psi phi. In 1.7 fb^-1 of data collected with the CDF II detector at the Tevatron ppbar collider we measure DeltaGamma = 0.076 +0.059-0.063 (stat.) +- 0.006 (syst.) ps^-1, well consistent with the Standard Model prediction, and a mean Bs lifetime of ctau_s = 456 +-13 (stat.) +- 7 (syst.) m^-6. We find no evidence for CP violation.

hep-ex↗