-
J. Adam,
X. Bai,
A. M. Baldini,
E. Baracchini,
C. Bemporad,
G. Boca,
P. W. Cattaneo,
G. Cavoto,
F. Cei,
C. Cerri, [......],
F. Tenchini,
C. Topchyan,
Y. Uchiyama,
R. Valle C. Voena,
F. Xiao,
S. Yamada,
S. Yamamoto,
S. Yamashita,
Yu. V. Yudin,
D. Zanello
[show abstract]
[hide abstract]
ABSTRACT: 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 $\mu^+$ 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.
03/2013;
-
MEG Collaboration,
J. Adam,
X. Bai,
A. M. Baldini,
E. Baracchini,
C. Bemporad,
G. Boca,
P. W. Cattaneo,
G. Cavoto,
F. Cei, [......],
Y. Uchiyama,
R. Valle,
C. Voena,
F. Xiao,
S. Yamada,
A. Yamamoto,
S. Yamashita,
Z. You,
Yu. V. Yudin,
D. Zanello
[show abstract]
[hide abstract]
ABSTRACT: 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.
03/2013;
-
A. M. Baldini,
F. Cei,
C. Cerri,
S. Dussoni,
L. Galli,
M. Grassi,
D. Nicolò,
F. Raffaelli,
F. Sergiampietri,
G. Signorelli, [......],
S. Ritt,
A. Stoykov,
T. I. Kang,
G. Lim,
W. Molzon,
Z. You,
N. Khomutov,
A. Korenchenko,
N. Kravchuk,
N. Kuchinksy
[show abstract]
[hide abstract]
ABSTRACT: 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 $6 \times 10^{-14}$
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.
01/2013;
-
J Adam,
X Bai,
A M Baldini,
E Baracchini,
C Bemporad,
G Boca,
P W Cattaneo,
G Cavoto,
F Cei,
C Cerri, [......],
C Topchyan,
Y Uchiyama,
R Valle,
C Voena,
F Xiao,
S Yamada,
A Yamamoto,
S Yamashita,
Yu V Yudin,
D Zanello
[show abstract]
[hide abstract]
ABSTRACT: 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-flavor-violating decay μ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.
Physical Review Letters 10/2011; 107(17):171801. · 7.37 Impact Factor
-
MEG collaboration,
J. Adam,
X Bai,
A. M. Baldini,
E Baracchini,
C Bemporad,
G. Boca,
P W Cattaneo,
G Cavoto,
F Cei, [......],
C. Topchyan,
Y. Uchiyama,
R. Valle,
C Voena,
F. Xiao,
S Yamada,
A Yamamoto,
S Yamashita,
Yu. V. Yudin,
D. Zanello
[show abstract]
[hide abstract]
ABSTRACT: 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.
07/2011;
-
[show abstract]
[hide abstract]
ABSTRACT: A thin superconducting solenoid is designed to provide a magnetic field of 1.5 T in the CMD-3 detector. The solenoid and an LXe calorimeter are placed in the common vacuum vessel of the detector. The solenoid is passively protected by subdivision and inductive coupling methods. The radiation thickness of the coil is 0.085X<sub>0</sub>, and the achieved E/M ratio is 6.9 kJ/kg. In 2007, the solenoid was tested in a prototype iron yoke, where the operational parameters were achieved. This paper reports the performance of the solenoid in the CMD-3 detector. The solenoid has been operated safely at a 1.35-T magnetic field. There were 19 quenches caused by various factors at magnetic fields in the range of 0.6-1.38 T. After a quench, the solenoid absorbed about 40% of the stored energy and warmed up to 42-55 K. A significant influence of quench-induced eddy currents on the detector design elements was observed. Liquid helium consumption at steady operation was about 3.5 L/h. Possible application of the achieved results to designing thinner solenoids is discussed.
IEEE Transactions on Appiled Superconductivity 11/2010; · 1.04 Impact Factor
-
R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
S. E. Baru,
N. S. Bashtovoy,
A. E. Bondar,
A. V. Bragin,
S. I. Eidelman,
D. A. Epifanov, [......],
A. S. Popov,
S. I. Redin,
A. A. Ruban,
N. M. Ryskulov,
Yu. M. Shatunov,
B. A. Shwartz,
A. L. Sibidanov,
I. G. Snopkov,
E P Solodov,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The $\phi$(1020) meson leptonic width has been determined from the combined
analysis of 4 major decay modes of the resonance ($\phi\to K^+
K^-,K^0_LK^0_S,\pi^+\pi^-\pi^0,\eta\gamma$) studied with the CMD-2 detector at
the VEPP-2M $e^+e^-$ collider. The following value has been obtained:
$\Gamma(\phi\to e^+e^-) = 1.235\pm 0.006\pm 0.022$ keV.
The $\phi(1020)$ meson parameters in four main decay channels have been also
recalculated: $B(\phi\to K^+K^-) = 0.493\pm 0.003\pm 0.007$, $B(\phi\to K_LK_S)
= 0.336\pm 0.002\pm 0.006$, $B(\phi\to\pi^+\pi^-\pi^0) = 0.155\pm 0.002\pm
0.005$, $B(\phi\to\eta\gamma) = 0.0138\pm 0.0002\pm 0.0002$.
10/2010;
-
MEG collaboration,
J. Adam,
X Bai,
A Baldini,
E Baracchini,
A. Barchiesi,
C Bemporad,
G. Boca,
P W Cattaneo,
G Cavoto, [......],
V. Tumakov,
Y. Uchiyama,
R. Valle,
C Voena,
F. Xiao,
S Yamada,
A Yamamoto,
S Yamashita,
Yu. V. Yudin,
D. Zanello
[show abstract]
[hide abstract]
ABSTRACT: 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. Comment: 13 pages, 9 figures. v2: improved estimate of photon reconstruction efficiency
08/2009;
-
R.M. Carey,
K.R. Lynch,
J.P. Miller,
B.L. Roberts,
W.M. Morse,
Y.K. Semertzides,
V.P. Druzhinin, B.I. Khazin,
I.A. Koop,
I. Logashenko,
S.I. Redin
[show abstract]
[hide abstract]
ABSTRACT: We propose to measure the muon anomalous magnetic moment, a{sub {mu}}, to 0.14 ppm-a fourfold improvement over the 0.54 ppm precision obtained in the BNL experiment E821. The muon anomaly is a fundamental quantity and its precise determination will have lasting value. The current measurement was statistics limited, suggesting that greater precision can be obtained in a higher-rate, next-generation experiment. We outline a plan to use the unique FNAL complex of proton accelerators and rings to produce high-intensity bunches of muons, which will be directed into the relocated BNL muon storage ring. The physics goal of our experiment is a precision on the muon anomaly of 16 x 10{sup -11}, which will require 21 times the statistics of the BNL measurement, as well a factor of 3 reduction in the overall systematic error. Our goal is well matched to anticipated advances in the worldwide effort to determine the standard model (SM) value of the anomaly. The present comparison, {Delta}a{sub {mu}} (Expt: -SM) = (295 {+-} 81) x 10{sup -11}, is already suggestive of possible new physics contributions to the muon anomaly. Assuming that the current theory error of 51 x 10{sup -11} is reduced to 30 x 10{sup -11} on the time scale of the completion of our experiment, a future {Delta}a{sub {mu}} comparison would have a combined uncertainty of {approx} 34 x 10{sup -11}, which will be a sensitive and complementary benchmark for proposed standard model extensions. The experimental data will also be used to improve the muon EDM limit by up to a factor of 100 and make a higher-precision test of Lorentz and CPT violation. We describe in this Proposal why the FNAL complex provides a uniquely ideal facility for a next-generation (g-2) experiment. The experiment is compatible with the fixed-target neutrino program; indeed, it requires only the unused Booster batch cycles and can acquire the desired statistics in less than two years of running. The proton beam preparations are largely aligned with the new Mu2e experimental requirements. The (g-2) experiment itself is based on the solid foundation of E821 at BNL, with modest improvements related to systematic error control. We outline the motivation, conceptual plans, and details of the tasks, anticipated budget, and timeline in this proposal.
01/2009;
-
G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G.T. Danby,
P T Debevec,
M. Deile,
H Deng, [......],
A Steinmetz,
L. R. Sulak,
C Timmermans,
A Trofimov,
D Urner,
P von Walter,
D. Warburton,
D Winn,
A Yamamoto,
D Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: Three independent searches for an electric dipole moment (EDM) of the positive and negative muons have been performed, using spin precession data from the muon g-2 storage ring at Brookhaven National Laboratory. Details on the experimental apparatus and the three analyses are presented. Since the individual results on the positive and negative muon, as well as the combined result, d=-0.1(0.9)E-19 e-cm, are all consistent with zero, we set a new muon EDM limit, |d| < 1.9E-19 e-cm (95% C.L.). This represents a factor of 5 improvement over the previous best limit on the muon EDM. Comment: 19 pages, 15 figures, 7 tables
11/2008;
-
V. M. Aul’chenko,
R. R. Akhmetshin,
B. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoi,
A. E. Bondar’,
A. V. Bragin,
A. A. Grebenyuk,
D. N. Grigor’ev,
D. A. Epifanov, [......],
A. L. Sibidanov,
V. P. Smakhtin,
I. G. Snopkov,
E. P. Solodov,
G. V. Fedotovich, B. I. Khazin,
Yu. M. Shatunov,
B. A. Shvarts,
S. I. Eidel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The ϕ → π+π−γγ and ϕ → π+π−η decays are sought in the experimental data obtained with the CMD-2 detector in the region of the ϕ-meson resonance. Upper
limits ℛ(ϕ → ππγγ)< 1.2 × 10−4 and ℛ(ϕ → ππη) < 6.1 × 10−5 (both at a C.L. of 90%) are determined for the branching ratios of these decays.
JETP Letters 08/2008; 88(2):85-90. · 1.35 Impact Factor
-
CMD-2 Collaboration: R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
S. E. Baru,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S. I. Eidelman, [......],
A. S. Popov,
S. I. Redin,
A. A. Ruban,
N. M. Ryskulov,
Yu. M. Shatunov,
B. A. Shwartz,
A. L. Sibidanov,
I. G. Snopkov,
E P Solodov,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The process e+ e- -> phi -> K+ K- has been studied with the CMD-2 detector using about 542 000 events detected in the center-of-mass energy range from 1.01 to 1.034 GeV. The systematic error of the cross section is estimated to be 2.2%. The phi(1020) meson parameters in the phi -> K+K- decay channel have been measured: sigma_0(phi-> K+K-) = 2016 +- 8 +- 44 nb, m(phi) = 1019.441 +- 0.008 +- 0.080 MeV/c2, Gamma(phi) = 4.24 +- 0.02 +- 0.03 MeV, B(e+e-)B(K+K-) = (14.27 +- 0.05 +- 0.31)*10(-5).
05/2008;
-
G W Bennett,
B Bousquet,
H N Brown,
G Bunce,
R M Carey,
P Cushman,
G T Danby,
P T Debevec,
M Deile,
H Deng, [......],
A Steinmetz,
L R Sulak,
C Timmermans,
A Trofimov,
D Urner,
P von Walter,
D Warburton,
D Winn,
A Yamamoto,
D Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: The spin precession frequency of muons stored in the (g-2) storage ring has been analyzed for evidence of Lorentz and CPT violation. Two Lorentz and CPT violation signatures were searched for a nonzero delta omega a(=omega a mu+ - omega a mu-) and a sidereal variation of omega a mu+/-). No significant effect is found, and the following limits on the standard-model extension parameters are obtained: bZ = -(1.0+/-1.1) x 10(-23) GeV; (m mu dZ0 + HXY)=(1.8+/-6.0) x 10(-23) GeV; and the 95% confidence level limits b perpendicular mu+ <1.4 x 10(-24) GeV and b perpendicular mu- <2.6 x 10(-24) GeV.
Physical Review Letters 03/2008; 100(9):091602. · 7.37 Impact Factor
-
E. V. Anashkin,
V. M. Aul’chenko,
R. R. Akhmetshin,
V. Sh. Banzarov,
L. M. Barkov,
S. E. Baru,
N. S. Bashtovoi,
D. V. Bondarev,
A. E. Bondar’,
A. V. Bragin, [......],
V. E. Fedorenko,
G. V. Fedotovich, B. I. Khazin,
A. G. Shamov,
Yu. M. Shatunov,
B. A. Shvarts,
B. N. Shuvalov,
D. V. Chernyak,
S. I. Eidel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The CMD-2 cryogenic magnetic detector used in a set of experiments on the VEPP-2M electron-positron collider at energies as
great as 1.4 GeV is described. The design of the detector subsystems and the algorithms for reconstructing tracks in the drift
chamber and the CsI and BGO calorimeters are presented. The spatial and energy resolutions of the detector systems have been
determined from analysis of experimental data. The design of the superconducting solenoid and the layout of its powering by
means of a superconducting transformer are shown. The trigger system of the detector and the conditions for recording “charged”
and “neutral” events on a magnetic tape are described. The procedure used to monitor the parameters of the detector systems
during the experiment is presented.
Instruments and Experimental Techniques 11/2006; 49(6):798-814. · 0.36 Impact Factor
-
The CMD-2 Collaboration: R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S K Dhawan,
S. I. Eidelman, [......],
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V.P. Smakhtin,
I. G. Snopkov,
E P Solodov,
J. A. Thompson,
Yu. V. Yudin,
A. S. Zaitsev,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the pion form factor based on e+e- annihilation data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five times larger than that used in our previous measurement.
11/2006;
-
R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S K Dhawan,
S. I. Eidelman, [......],
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V.P. Smakhtin,
I. G. Snopkov,
E P Solodov,
J. A. Thompson,
Yu. V. Yudin,
A. S. Zaitsev,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: The cross section of the process e+e- -> pi+pi- has been measured at the CMD-2 detector in the 370-520 MeV center-of-mass (c.m.) energy range. A systematic uncertainty of the measurement is 0.7 %. Using all CMD-2 data on the pion form factor, the pion electromagnetic radius was calculated. The cross section of muon pair production was also determined.
11/2006;
-
R. R. Akhmetshin,
V. M. Aulchenko,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoy,
A. E. Bondar,
D. V. Bondarev,
A. V. Bragin,
S. I. Eidelman,
D. A. Epifanov, [......],
B. A. Shwartz,
A. L. Sibidanov,
V. A. Sidorov,
A. N. Skrinsky,
V. P. Smakhtin,
I. G. Snopkov,
E. P. Solodov,
Yu. V. Yudin,
A. S. Zaitsev,
S. G. Zverev
[show abstract]
[hide abstract]
ABSTRACT: The cross section of the process
ee→πππ
has been measured in the c.m. energy range 984 1060 MeV with the CMD-2
detector at the VEPP-2M collider. The obtained value of
Br(ϕ→ee)Br(ϕ→πππ)=(4.51±0.16±0.11)×10
is in good agreement with the previous measurements and has the best
accuracy. Analysis of the Dalitz plot was performed. The contributions
of the dominant ϕ→ρπ mechanism as well as of a small
direct ϕ→3π amplitude were determined.
Physics Letters B 10/2006; 642:203-209. · 3.95 Impact Factor
-
G. W. Bennett,
B. Bousquet,
H. N. Brown,
G. Bunce,
R. M. Carey,
P. Cushman,
G. T. Danby,
P. T. Debevec,
M. Deile,
H. Deng, [......],
A. Steinmetz,
L. R. Sulak,
C. Timmermans,
A. Trofimov,
D. Urner,
P. von Walter,
D. Warburton,
D. Winn,
A. Yamamoto,
D. Zimmerman
[show abstract]
[hide abstract]
ABSTRACT: We present the final report from a series of precision measurements of the muon anomalous magnetic moment, aμ=(g-2)/2. The details of the experimental method, apparatus, data taking, and analysis are summarized. Data obtained at Brookhaven National Laboratory, using nearly equal samples of positive and negative muons, were used to deduce aμ(Expt)=11659208.0(5.4)(3.3)×10-10, where the statistical and systematic uncertainties are given, respectively. The combined uncertainty of 0.54 ppm represents a 14-fold improvement compared to previous measurements at CERN. The standard model value for aμ includes contributions from virtual QED, weak, and hadronic processes. While the QED processes account for most of the anomaly, the largest theoretical uncertainty, ≈0.55 ppm, is associated with first-order hadronic vacuum polarization. Present standard model evaluations, based on e+e- hadronic cross sections, lie 2.2–2.7 standard deviations below the experimental result.
Phys. Rev. D. 04/2006; 73(7).
-
V. M. Aul’chenko,
R. R. Akhmetshin,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoĭ,
D. V. Bondarev,
A. E. Bondar’,
A. V. Bragin,
N. I. Gabyshev,
D. A. Gorbachev, [......],
E. P. Solodov,
J. A. Thompson,
G. V. Fedotovich, B. I. Khazin,
V. W. Hughes,
A. G. Shamov,
Yu. M. Shatunov,
B. A. Shvarts,
S. I. Éĭdel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The results of the experiment on the measurement of the e
+
e
− → π+π− cross section in a cm energy range of 370–520 MeV are presented. The systematic measurement error is equal to 0.7%. In the
vector dominance model, the pion electromagnetic radius is calculated using all the CMD-2 data on the pion form factor. The
cross section for the production of a muon pair is measured in the energy range of the experiment.
JETP Letters 01/2006; 84(8):413-417. · 1.35 Impact Factor
-
V. M. Aul’chenko,
R. R. Akhmetshin,
V. Sh. Banzarov,
L. M. Barkov,
N. S. Bashtovoi,
D. V. Bondarev,
A. E. Bondar’,
A. V. Bragin,
A. A. Valishev,
N. I. Gabyshev, [......],
E. P. Solodov,
J. A. Thompson,
G. V. Fedotovich, B. I. Khazin,
V. W. Hughes,
A. G. Shamov,
Yu. M. Shatunov,
B. A. Shwartz,
S. I. Éidel’man,
Yu. V. Yudin
[show abstract]
[hide abstract]
ABSTRACT: The cross section for the process e
+
e
− → π+π− is measured in the c.m. energy range 1.04—1.38 GeV by analyzing 995 000 selected collinear events including 860000 e
+
e
− events, 82000 μ+μ− events, and 33000 π+π− events. The systematic and statistical errors of measuring the pion form factor are equal to 1.2–4.2 and 5–13%, respectively.
JETP Letters 11/2005; 82(12):743-747. · 1.35 Impact Factor
