646 research outputs found
Investigating The Physics Case of Running a B-Factory at the Y(5S) Resonance
We discuss the physics case of a high luminosity B-Factory running at the
Y(5S) resonance. We show that the coherence of the B meson pairs is preserved
at this resonance, and that Bs can be well distinguished from Bd and charged B
mesons. These facts allow to cover the physics program of a traditional
B-Factory and, at the same time, to perform complementary measurements which
are not accessible at the Y(4S). In particular we show how, despite the
experimental limitations in performing time-dependent measurements of Bs
decays, the same experimental information can be extracted, in several cases,
from the determination of time-integrated observables. In addition, a few
examples of the potentiality in measuring rare Bs decays are given. Finally, we
discuss how the study of Bs meson will improve the constraints on New Physics
parameters in the Bs sector, in the context of the generalized Unitarity
Triangle analysis.Comment: 47 pages, 22 figure
Single-hit resolution measurement with MEG II drift chamber prototypes
Drift chambers operated with helium-based gas mixtures represent a common
solution for tracking charged particles keeping the material budget in the
sensitive volume to a minimum. The drawback of this solution is the worsening
of the spatial resolution due to primary ionisation fluctuations, which is a
limiting factor for high granularity drift chambers like the MEG II tracker. We
report on the measurements performed on three different prototypes of the MEG
II drift chamber aimed at determining the achievable single-hit resolution. The
prototypes were operated with helium/isobutane gas mixtures and exposed to
cosmic rays, electron beams and radioactive sources. Direct measurements of the
single hit resolution performed with an external tracker returned a value of
110 m, consistent with the values obtained with indirect measurements
performed with the other prototypes.Comment: 18 pages, 18 figure
Performance of Optically Readout GEM-based TPC with a 55Fe source
Optical readout of large Time Projection Chambers (TPCs) with multiple Gas
Electron Multipliers (GEMs) amplification stages has shown to provide very
interesting performances for high energy particle tracking. Proposed
applications for low-energy and rare event studies, such as Dark Matter search,
ask for demanding performance in the keV energy range. The performance of such
a readout was studied in details as a function of the electric field
configuration and GEM gain by using a Fe source within a 7 litre
sensitive volume detector developed as a part of the R\&D for the CYGNUS
project. Results reported in this paper show that the low noise level of the
sensor allows to operate with a 2~keV threshold while keeping a rate of
fake-events lesser than 10 per year. In this configuration, a detection
efficiency well above 95\% along with an energy resolution () of 18\%
is obtained for the 5.9 keV photons, demonstrating the very promising
capabilities of this technique
Rare Semileptonic Decays of Heavy Mesons with Flavor SU(3) Symmetry
In this paper, we calculate the decay rates of , , , and
semileptonic decay processes, in which only the light
quarks decay, while the heavy flavors remain unchanged. The branching ratios of
these decay processes are calculated with the flavor SU(3) symmetry. The
uncertainties are estimated by considering the SU(3) breaking effect. We find
that the decay rates are very tiny in the framework of the Standard Model. We
also estimate the sensitivities of the measurements of these rare decays at the
future experiments, such as BES-III, super- and LHC-.Comment: 4 pages and 1 figure, accepted by European Physical Journal
MPGD Optical Read Out for Directional Dark Matter Search
The Time Projection method is an ideal candidate to track low energy release particles. Large volumes can be readout by means of a moderate number of channels providing a complete 3D reconstruction of the charged tracks within the sensitive volume. It allows the measurement not only of the total released energy but also of the energy release density along the tracks that can be very useful for particle identification and to solve the head-tail ambiguity of the tracks. Moreover, gas represents a very interesting target to study Dark Matter interactions. In gas, nuclear recoils can travel enough to give rise to tracks long enough to be acquired and reconstructed
A 1 m Gas Time Projection Chamber with Optical Readout for Directional Dark Matter Searches: the CYGNO Experiment
The aim of the CYGNO project is the construction and operation of a 1~m
gas TPC for directional dark matter searches and coherent neutrino scattering
measurements, as a prototype toward the 100-1000~m (0.15-1.5 tons) CYGNUS
network of underground experiments. In such a TPC, electrons produced by
dark-matter- or neutrino-induced nuclear recoils will drift toward and will be
multiplied by a three-layer GEM structure, and the light produced in the
avalanche processes will be readout by a sCMOS camera, providing a 2D image of
the event with a resolution of a few hundred micrometers. Photomultipliers will
also provide a simultaneous fast readout of the time profile of the light
production, giving information about the third coordinate and hence allowing a
3D reconstruction of the event, from which the direction of the nuclear recoil
and consequently the direction of the incoming particle can be inferred. Such a
detailed reconstruction of the event topology will also allow a pure and
efficient signal to background discrimination. These two features are the key
to reach and overcome the solar neutrino background that will ultimately limit
non-directional dark matter searches.Comment: 5 page, 7 figures, contribution to the Conference Records of 2018
IEEE NSS/MI
MEG Upgrade Proposal
We propose the continuation of the MEG experiment to search for the charged
lepton flavour violating decay (cLFV) \mu \to e \gamma, 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
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.Comment: A. M. Baldini and T. Mori Spokespersons. Research proposal submitted
to the Paul Scherrer Institute Research Committee for Particle Physics at the
Ring Cyclotron. 131 Page
Measurement of the radiative decay of polarized muons in the MEG experiment
We studied the radiative muon decay by
using for the first time an almost fully polarized muon source. We identified a
large sample (~13000) of these decays in a total sample of 1.8x10^14 positive
muon decays collected in the MEG experiment in the years 2009--2010 and
measured the branching ratio B() =
(6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV,
consistent with the Standard Model prediction. The precise measurement of this
decay mode provides a basic tool for the timing calibration, a normalization
channel, and a strong quality check of the complete MEG experiment in the
search for process.Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which
was recently calculated. Published versio
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