Rare decays at hadron colliders

Rare lepton decays of the B0(s) mesons are sensitive probes of New Physics. The search for the decays B0(s)→ μ+μ− may provide information on the presence of new (pseudo-) scalar particles. Also the study of the electroweak penguin processes are powerful probes for new physics, as physics beyond the Standard Model (SM) can enter via virtual particles at the same level as SM physics. The Tevatron collider opened the way to high precision Heavy Flavor physics at hadron collider experiments, while the LHCb experiment definitively proved the physics performances are competitive with the B-factories. This is a short review of the searches of rare decays performed at the hadron colliders

Precision Measurement of KS Meson Lifetime with the KLOE detector

Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DaFne, we have measured the KS lifetime. From a fit to the proper time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This is the most precise measurement today in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the Ks.Comment: 5 pages, 7 figure

A Study of the Radiative Ke3 Decay and Search for Direct Photon Emission with the KLOE Detector

We present a measurement of the ratio R = \Gamma(\keg;\Estar>30\mev,\qstar>20^\circ)$/$\Gamma(\kegf)$and a first measurement of the direct emission contribution in KL semileptonic decays. The measurement is done at the DAFNE phi-factory selecting phi->KL KS decays with the KLOE detector. We use 328 pb^{-1}$ of data corresponding to about 3.5 million Ke3(g) events and about 9000 radiative events. Our result is R=(924 +/- 23(stat) +/-16(syst)10^{-5} for the branching ratio and X=-2.3 +/- 1.3(stat) +/- 1.4(syst) for the parameter describing direct emission.Comment: 8 pages, 7 figure

A global fit to determine the pseudoscalar mixing angle and the gluonium content of the eta' meson

We update the values of the eta-eta' mixing angle and of the eta' gluonium content by fitting our measurement R_phi = BR(phi to eta' gamma)/ BR(phi to eta gamma) together with several vector meson radiative decays to pseudoscalars (V to P gamma), pseudoscalar mesons radiative decays to vectors (P to V gamma) and the eta' to gamma gamma, pi^0 to gamma gamma widths. From the fit we extract a gluonium fraction of Z^2_G = 0.12 +- 0.04, the pseudoscalar mixing angle psi_P = (40.4 +- 0.6) degree and the phi-omega mixing angle psi_V = (3.32 +- 0.09) degree. Z^2_G and psi_P are fairly consistent with those previously published. We also evaluate the impact on the eta' gluonium content determination of future experimental improvements of the eta' branching ratios and decay width.Comment: 13 pages, 7 figures to submit to JHE

Measurement of the η→3π0\eta\to 3\pi^{0} slope parameter α\alpha with the KLOE detector

We present a measurement of the slope parameter $\alpha$ for the $\eta\to 3\pi^{0}$ decay, with the KLOE experiment at the DA$\Phi$NE $\phi$-factory, based on a background free sample of $\sim$ 17 millions $\eta$ mesons produced in $\phi$ radiative decays. By fitting the event density in the Dalitz plot we determine $\alpha = -0.0301 \pm 0.0035\,stat\;_{-0.0035}^{+0.0022}\,syst\,$. The result is in agreement with recent measurements from hadro- and photo-production experiments.Comment: 14 pages, 11 figure

Measurement of the K_L \to \pi\mu\nu form factor parameters with the KLOE detector

Using 328 pb^{-1}of data collected at DAFNE corresponding to $\sim$ 1.8 million $K_L\to \pi\mu\nu$ decays, we have measured the $K_{\mu 3}$ form factor parameters. The structure of the $K-\pi$ vector-current provides information about the dynamics of the strong interaction; its knowledge is necessary for evaluation of the phase-space integral required for measuring the CKM matrix element $V_{us}$ and for testing lepton universality in kaon decays. Using a new parametrization for the vector and scalar form factors, we find $\lambda_+$=\pt(25.7\pm 0.6),-3, and $\lambda_0$=\pt(14.0\pm 2.1),-3,. Our result for $\lambda_0$, together with recent lattice calculations of $f_\pi$, $f_K$ and $f(0)$, satisfies the Callan-Trieman relatio

Measurement of the absolute branching ratios for semileptonic K+/- decays with the KLOE detector

Using a sample of over 600 million phi->K+K- decays collected at the Dafne e+e- collider, we have measured with the KLOE detector the absolute branching ratios for the charged kaon semileptonic decays, K+/- -> p0 e nu (gamma) (Ke3) and K+/- -> p0 mu nu (gamma) (Kmu3). The results, BR(Ke3) = 0.04965 +/- 0.00038_{stat} +/- 0.00037_{syst} and BR(Kmu3) = 0.03233 +/- 0.00029_{stat} +/- 0.00026_{syst}, are inclusive of radiation. Accounting for correlations, we derive the ratio Kmu3/Ke3 = 0.6511+/-0.0064. Using the semileptonic form factors measured in the same experiment, we obtain V_{us}f_{+}(0) = 0.2141 +/- 0.0013.Comment: 13 pages, 3 figures, submitted to JHEP. v2: minor revisions required by JHEP, v3: final version published by JHEP (replacement of 2 incorrect affiliations)link: http://www.iop.org/EJ/abstract/1029-8479/2008/02/09

Measurement of the front-end dead-time of the LHCb muon detector and evaluation of its contribution to the muon detection inefficiency

A method is described which allows to deduce the dead-time of the front-end electronics of the LHCb muon detector from a series of measurements performed at different luminosities at a bunch-crossing rate of 20 MHz. The measured values of the dead-time range from 70 ns to 100 ns. These results allow to estimate the performance of the muon detector at the future bunch-crossing rate of 40 MHz and at higher luminosity