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# Search results

382 records were found.

## Silicon Photo-Multiplier radiation hardness tests with a beam controlled neutron source

Comment: 7 pages, 6 figures, Submitted to Nucl. Inst. Meth. A

## Overview of LHCb alignment

In this report, we review the alignment strategy for the LHCb detector. We discuss the internal alignment stategy for each subdetector and the alignment of each of the subdetectors relative to one another.

## Measurement of the branching ratios $\psi^\prime \to e^+ e^-$, $\psi^\prime \to J/\psi \pi \pi$ and $\psi^\prime \to J/\psi \eta$

We have measured several branching ratios for $\psi^\prime$ decay using the data collected by FNAL E835 experiment during year 2000, obtaining ${\cal B}(\psi^\prime \to e^+ e^-) = 0.0068\pm0.0001\pm0.0004$, ${\cal B}(\psi^\prime \to J/\psi \pi^+ \pi^-) = 0.292\pm0.005\pm0.018$, ${\cal B}(\psi^\prime \to J/\psi \pi^0 \pi^0) = 0.167\pm0.005\pm0.014$ and ${\cal B}(\psi^\prime \to J/\psi \eta) = 0.028\pm0.002\pm0.002$. We also present a measurement of the dipion mass distribution in the decays $\psi^\prime \to J/\psi \pi \pi$.

## Precision measurements of the total and partial widths of the psi(2S) charmonium meson with a new complementary-scan technique in antiproton-proton annihilations

Comment: 17 pages, 3 figures, 3 tables. Final manuscript accepted for publication in Phys. Lett. B. Parts of the text slightly expanded or rearranged; results are unchanged

## Performance of the LHCb muon system with cosmic rays

Comment: Submitted to JINST and accepted

## Precision measurement of the ratio BR(K_s→ π^+ π^- e^+ e^- )BR (K_L→π^+ π^- π_D^0)

The KS→π+π−e+e− decay mode was investigated using the data collected in 2002 by the NA48/1 collaboration. With about 23 k KS→π+π−e+e− events and 59 k View the MathML source normalization decays, the KS→π+π−e+e− branching ratio relative to the View the MathML source one was determined to be View the MathML source. This result was used to set the upper limit |gE1/gBR|<3.0 at 90% CL on the presence, in the decay amplitude, of an E1 direct emission (gE1) term relative to the dominant inner bremsstrahlung (gBR) term. The CP-violating asymmetry View the MathML source in the View the MathML source distribution of KS→π+π−e+e− events, where phi is the angle between the π+π− and the e+e− decay planes in the kaon centre of mass, was found to be View the MathML source, consistent with zero. These results are in good agreement with a description of...

## Measurement of the direct emission and interference terms and search for CP violation in the decay K ±→π ± π 0 γ

We report on the measurement of the direct emission (DE) and interference (INT) terms of the K ±→π ± π 0 γ decay by the NA48/2 experiment at the CERN SPS. From the data collected during 2003 and 2004 about 600k such decay candidates have been selected. The relative amounts of DE and INT with respect to the internal bremsstrahlung (IB) contribution have been measured in the range MeV: where is the kinetic energy of the charged pion in the kaon rest frame. This is the first observation of an interference term in K ±→π ± π 0 γ decays, thus allowing the normalised electric and magnetic amplitudes to be measured, giving X E =(−24±6) GeV−4, and X M =(254±9) GeV−4. In addition, a limit on the CP violating asymmetry in the K + and K − branching ratios for this channel has been determined to be less than 1.5×10−3 at 90% confidence level.

## Empirical parameterization of the K±→π±π0π0 decay Dalitz plot

As first observed by the NA48/2 experiment at the CERN SPS, the π0π0 invariant mass (M00) distribution from K±→π±π0π0 decay shows a cusp-like anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the ππ scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively, has been recently reported. In the present work the Dalitz plot of this decay is fitted to a new empirical parameterization suitable for practical purposes, such as Monte Carlo simulations of K±→π±π0π0 decays.

## New high statistics measurement of $K_{e4}$ decay form factors and $\pi\pi$ scattering phase shifts

We report results from a new measurement of the $K_{e4}$ decay $K^{\pm} \pi^{+}\pi^{-}e^{\pm}\nu$ by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 $K_{e4}$ decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and $\pi\pi$ phase difference ($\delta=\delta_s-\delta_p$) have been measured in ten independent bins of the $\pi\pi$ mass spectrum to investigate their variation. A sizeable acceptance at large $\pi\pi$ mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the $\pi\pi$ scattering lengths a00 and a20 . Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in th...

## First Observation and Measurement of the Decay K+- -> pi+- e+ e- gamma

Using the full data set of the NA48/2 experiment, the decay K+- -> pi+- e+ e- gamma is observed for the first time, selecting 120 candidates with 7.3 +- 1.7 estimated background events. With K+- -> pi+- pi0D as normalisation channel, the branching ratio is determined in a model-independent way to be Br(K+- -> pi+- e+ e- gamma, m_eegamma > 260 MeV/c^2) = (1.19 +- 0.12_stat +- 0.04_syst) x 10^-8. This measured value and the spectrum of the e+ e- gamma invariant mass allow a comparison with predictions of Chiral Perturbation Theory.