arXiv subjects

C. Cerri

Publications and source records attributed to C. Cerri.

14 recordsLinked to original sources

arXiv2023

First observation and study of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay

The NA48/2 experiment at CERN reports the first observation of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay based on a sample of 2437 candidates with 15% background contamination collected in 2003--2004. The decay branching ratio in the kinematic region of the squared dilepton mass above $0.03$~GeV$^2/c^4$ is measured to be $(0.65 \pm 0.03) \times 10^{-6}$. The extrapolation to the full kinematic space, using a specific model, is found to be $(3.45 \pm 0.16) \times 10^{-6}$, in agreement with chiral perturbation theory predictions.

hep-ex↗

arXiv2018

Search for $K^{+}\rightarrowπ^{+}ν\overlineν$ at NA62

$K^{+}\rightarrowπ^{+}ν\overlineν$ is one of the theoretically cleanest meson decay where to look for indirect effects of new physics complementary to LHC searches. The NA62 experiment at CERN SPS is designed to measure the branching ratio of this decay with 10\% precision. NA62 took data in pilot runs in 2014 and 2015 reaching the final designed beam intensity. The quality of 2015 data acquired, in view of the final measurement, will be presented.

hep-ex↗

arXiv2016

ChPT tests at the NA48 and NA62 experiments at CERN

The NA48/2 Collaboration at CERN has accumulated unprecedented statistics of rare kaon decays in the Ke4 modes: Ke4(+-) ($K^\pm \to π^+ π^- e^\pm ν$) and Ke4(00) ($K^\pm \to π^0 π^0 e^\pm ν$) with nearly one percent background contamination. The detailed study of form factors and branching rates, based on these data, has been completed recently. The results brings new inputs to low energy strong interactions description and tests of Chiral Perturbation Theory (ChPT) and lattice QCD calculations. In particular, new data support the ChPT prediction for a cusp in the $π^0π^0$ invariant mass spectrum at the two charged pions threshold for Ke4(00) decay. New final results from an analysis of about 400 $K^\pm \to π^\pm γγ$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN during low intensity runs with minimum bias trigger configurations are presented. The results include a model-independent decay rate measurement and fits to ChPT description.

hep-ex↗

arXiv2014

Prospects for $K^+ \to π^+ ν\bar{ ν}$ at CERN in NA62

The NA62 experiment will begin taking data in 2015. Its primary purpose is a 10% measurement of the branching ratio of the ultrarare kaon decay $K^+ \to π^+ ν\bar{ ν}$, using the decay in flight of kaons in an unseparated beam with momentum 75 GeV/c.The detector and analysis technique are described here.

hep-ex↗

arXiv2014

Recent NA48/2 and NA62 results

The NA48/2 Collaboration at CERN has accumulated and analysed unprecedented statistics of rare kaon decays in the $K_{e4}$ modes: $K_{e4}(+-)$ ($K^\pm \to π^+ π^- e^\pm ν$) and $K_{e4}(00)$ ($K^\pm \to π^0 π^0 e^\pm ν$) with nearly one percent background contamination. It leads to the improved measurement of branching fractions and detailed form factor studies. New final results from the analysis of 381 $K^\pm \to π^\pm γγ$ rare decay candidates collected by the NA48/2 and NA62 experiments at CERN are presented. The results include a decay rate measurement and fits to Chiral Perturbation Theory (ChPT) description.

hep-ex↗

arXiv2013

New constraint on the existence of the mu+-> e+ gamma decay

The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons on target, in the search for the lepton flavour violating decay mu^+ -> e^+ gamma is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 \times 10^-13 (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG.

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arXiv2013

The MEG detector for $μ+\to e+γ$ decay search

The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\ by using one of the most intense continuous $μ^+$ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus.

physics.ins-det↗

arXiv2013

MEG Upgrade Proposal

We propose the continuation of the MEG experiment to search for the charged lepton flavour violating decay (cLFV) μ\to e γ, based on an upgrade of the experiment, which aims for a sensitivity enhancement of one order of magnitude compared to the final MEG result, down to the $6 \times 10^{-14}$ level. The key features of this new MEG upgrade are an increased rate capability of all detectors to enable running at the intensity frontier and improved energy, angular and timing resolutions, for both the positron and photon arms of the detector. On the positron-side a new low-mass, single volume, high granularity tracker is envisaged, in combination with a new highly segmented, fast timing counter array, to track positron from a thinner stopping target. The photon-arm, with the largest liquid xenon (LXe) detector in the world, totalling 900 l, will also be improved by increasing the granularity at the incident face, by replacing the current photomultiplier tubes (PMTs) with a larger number of smaller photosensors and optimizing the photosensor layout also on the lateral faces. A new DAQ scheme involving the implementation of a new combined readout board capable of integrating the diverse functions of digitization, trigger capability and splitter functionality into one condensed unit, is also under development. We describe here the status of the MEG experiment, the scientific merits of the upgrade and the experimental methods we plan to use.

physics.ins-det↗

arXiv2013

Measurement of the branching ratio of the decay $Ξ^{0}\rightarrow Σ^{+} μ^{-} \barν_μ$

From the 2002 data taking with a neutral kaon beam extracted from the CERN-SPS, the NA48/1 experiment observed 97 $Ξ^{0}\rightarrow Σ^{+} μ^{-} \barν_μ$ candidates with a background contamination of $30.8 \pm 4.2$ events. From this sample, the BR($Ξ^{0}\rightarrow Σ^{+} μ^{-} \barν_μ$) is measured to be $(2.17 \pm 0.32_{\mathrm{stat}}\pm 0.17_{\mathrm{syst}})\times10^{-6}$.

hep-ex↗

arXiv2011

New limit on the lepton-flavour violating decay mu -> e gamma

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton flavour violating decay mu->e gamma. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8 x 10**14 muon decays, gives a 90% C.L. upper limit of 2.4 x 10**-12 on the branching ratio of the mu->e gamma decay, constituting the most stringent limit on the existence of this decay to date.

hep-ex↗

arXiv2010

Empirical parameterization of the K+- -> pi+- pi0 pi0 decay Dalitz plot

As first observed by the NA48/2 experiment at the CERN SPS, the $\p0p0$ invariant mass (M00) distribution from $\kcnn$ decay shows a cusp-like anomaly at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi 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+- -> pi+- pi0 pi0 decays.

hep-ex↗

arXiv2010

A limit for the mu -> e gamma decay from the MEG experiment

A search for the decay mu -> e gamma, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of BR(mu -> e gamma) < 2.8 x 10**-11 (90% C.L.). This corresponds to the measurement of positrons and photons from ~ 10**14 stopped mu-decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector.

hep-ex↗

arXiv2003

The CDFII Time-Of-Flight Detector and Impact on Beauty Flavor Tagging

The new CDFII detector incorporates a Time-of-Flight detector (TOF), employing plastic scintillator bars and fine-mesh photomultipliers. Since August 2001 the TOF system has been fully instrumented and integrated into the CDFII data acquisition system. With a design goal of $100 ps$ resolution the TOF system will provide at least two standard deviations separation between $K^{\pm}$ and $π^{\pm}$ for momenta $p<1.6 GeV/c$, complementing low momentum particle identification by means of the specific ionization energy loss measured in the drift chamber. We describe the design of the TOF detector and discuss the current status of its calibration and initial performances. Finally we review the expected impact of the TOF detector in the flavor tagging of neutral $B_S$ meson.

hep-ex↗

arXiv1994

Determination of the branching ratios $Γ(K_L \to 3 π^0) / Γ(K_L \to π^+ π^- π^0)$ and $Γ(K_L \to 3 π^0) / Γ(K_L \to πe ν)$

Improved branching ratios were measured for the $K_L \to 3 π^0 $ decay in a neutral beam at the CERN SPS with the NA31 detector: $Γ(K_L \to 3 π^0) / Γ(K_L \to π^+ π^- π^0) = 1.611 \pm 0.037$ and $Γ(K_L \to 3 π^0) / Γ(K_L \to πe ν) = 0.545 \pm 0.010$. From the first number an upper limit for $ΔI =5/2$ and $ΔI = 7/2 $ transitions in neutral kaon decay is derived. Using older results for the Ke3/K$μ$3 fraction, the 3$π^0$ branching ratio is found to be $Γ(K_L \to 3 π^0 )/ Γ_{tot} = (0.211 \pm 0.003)$, about a factor three more precise than from previous experiments.

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