We report a measurement of the positive muon lifetime to a precision of 1.0 ppm; it is the most precise particle lifetime ever measured. The experiment used a time-structured, low-energy muon beam ...and a segmented plastic scintillator array to record more than 2×10(12) decays. Two different stopping target configurations were employed in independent data-taking periods. The combined results give τ(μ(+)) (MuLan)=2 196 980.3(2.2) ps, more than 15 times as precise as any previous experiment. The muon lifetime gives the most precise value for the Fermi constant: G(F) (MuLan)=1.166 378 8(7)×10(-5) GeV(-2) (0.6 ppm). It is also used to extract the μ(-)p singlet capture rate, which determines the proton's weak induced pseudoscalar coupling g(P).
The anomalous magnetic moment of the muon, aμ, is a unique quantity that allows high-precision tests of the Standard Model. Currently, a difference of 3 to 4 standard deviations is observed between ...the prediction of the Standard Model and the most precise measurement performed. We present a review of the Standard Model calculations of aμ. The principles and history of aμ experiments are presented, and the recent measurement at the Brookhaven National Laboratory, USA, is described in detail. Prospects for further improving the accuracy of both calculations and measurements of aμ are discussed.
The article describes the design of a digital model of an HPC system for processing data from the Super Charm-Tau factory electron-positron collider of the "megascience" class. This model is ...developed using the AGNES multiagent modeling platform. The model includes intelligent agents that mimic the behavior of the main subsystems of the supercomputer, such as a task scheduler, computing clusters, data storage system, etc. This model allows calculating the parameters of the computing system necessary for processing and storing the results of operation of the Super Charm-Tau factory after its commissioning.
Micro-pattern gas technology is planned for the upgrade of the tracking system of the CMD-3 detector at the VEPP-2000 electron-positron collider in Budker INP. The upgrade includes a new cylinder ...tracking and trigger detector that consists of two tracking layers at a radius of 32 to 33 cm with coordinate resolution close to 0.1 mm in Z (along the beam axis) and trigger segments of about 1 cm in phi. Another new coordinate subsystem includes two end-cap discs with active area between radius of 50 mm and 250 mm, that provides spatial resolution in R and in phi close to 1 mm as well as trigger signal from the phi segments. For these two subsystems we plan to use micro-RWELL technology because it allows much simpler assembling of large cylindrical detector and large discs due to more rigid glass-fiber support as compared to the triple GEM technology. The new cylindrical detector and end-cap discs of the CMD-3 are considered as a prototypes of the Inner Tracker of the detector for the future Super C-Tau Factory (SCTF) at Budker INP. The SCTF is an electron-positron collider for the energy range of 3-7 GeV in the center of mass system that will provide luminosity of 1035 cm−2s−1. Coordinate system of the detector for the SCTF will include among other systems, the Inner Tracker and the end-cap discs. The Inner Tracker will be 60 cm long and occupy radius up to 20 cm, while the end-cap discs will have radius up to 180 cm and will have to provide trigger signal. For the end-cap discs the MPGD option is considered based either on the triple-GEM or on the micro-RWELL, while for the Inner Tracker three main options are competing: compact Time Projection Chamber, silicon micro-strip tracker and cylindrical MPGD tracker. The first results of simulations with all these options are presented with preliminary discussion about the choice of the option.
A
bstract
The cross section of the process
e
+
e
−
→ ηπ
+
π
−
is measured using the data collected with the CMD-3 detector at the VEPP-2000 collider in the center-of-mass energy range from 1
.
1 to 2
....
0 GeV. The decay mode
η → γγ
is used for
η
meson reconstruction in the data sample corresponding to an integrated luminosity of 78
.
3 pb
−
1
. The energy dependence of the
e
+
e
−
→ ηπ
+
π
−
cross section is fitted within the framework of vector meson dominance in order to extract the Γ(
ρ
(1450)
→ e
+
e
−
)
B
(
ρ
(1450)
→ ηπ
+
π
−
) and the Γ(
ρ
(1700)
→ e
+
e
−
)
B
(
ρ
(1700)
→ ηπ
+
π
−
) products. Based on conservation of vector current, the analyzed data are used to test the relationship between the
e
+
e
−
→ ηπ
+
π
−
cross section and the spectral function in
τ
−
→ ηπ
−
π
0
ντ
decay. The
e
+
e
−
→ ηπ
+
π
−
cross section obtained with the CMD-3 detector is in good agreement with the previous measurements.
One of the goals of the Cryogenic Magnetic Detector at Budker Institute of Nuclear Physics SB RAS (Novosibirsk, Russia) is a study of hadron production in electron-positron collisions near threshold. ...The neutron-antineutron pair production events can be detected only by the calorimeters. In the barrel calorimeter the antineutron annihilation typically occurs about 5 ns or later after the beams crossing. For identification of such events it is necessary to measure the time of flight of particles to the LXe-calorimeter with an accuracy of about a few nanoseconds. The LXe-calorimeter consists of 14 layers of ionization chambers with two readout: anode and cathode. The duration of charge collection to the anodes is about 4.5 mus, while the required accuracy of measuring of the signal arrival time is less than 1/1000 of that (i.e. 4.5 ns). Besides, the signals' shapes differ substantially from event to event, so the signal arrival time is measured in two stages. In the paper we describ the development of the special electronics which performs waveform digitization and the on-line measurement of signals' arrival times and amplitudes.
Recent results from CMD-3 Ignatov, F. V.; Akhmetshin, R. R.; Amirkhanov, A. N. ...
EPJ Web of Conferences,
2019, Letnik:
212
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
Regular data taking with the CMD-3 at the electron-positron collider VEPP-2000 is under way since 2010. The collected data sample corresponds to about 200 inverse picobarns of integrated luminosity ...per detector in the energy range from 0.32 up to 2 GeV, with a goal to collect about 1
fb
−1
during next five years. Some of the recent results from the CMD-3 detector are discussed.
Calorimetry of the CMD-3 detector Akhmetshin, R R; Anisenkov, A V; Aulchenko, V M ...
Journal of physics. Conference series,
11/2017, Letnik:
928, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The CMD-3 detector has been collecting data since 2010 at the e+e− collider VEPP-2000 in the Budker Institute of Nuclear Physics. VEPP-2000 uses the novel round beam technique and provides high ...luminosity in a wide c.m.energy range from 0.32 to 2 GeV. The physics goal of the CMD-3 experiment is a study of the e+e− annihilation into hadrons. CMD-3 is a general-purpose detector, which provides high efficiency for both charged and neutral particles. The electromagnetic calorimeter consists of the barrel calorimeter based on liquid xenon and CsI crystals, and the endcap calorimeter based on BGO crystals. The main parameters of the calorimeters are presented.
A brief review of the recent results on the hadronic cross section measurements with the CMD-3 detector at the
e
+
e
−
collider VEPP-2000 is given. Focus is made on the processes with charged kaons ...in multihadron events, which have a strong impact on strange meson spectroscopy and form factors that are important ingredients in the Dalitz plot analysis. Experimental data relevant to the topic are presented from the broad energy range covered by VEPP-2000 and compared to earlier measurements by the different collaborations. The analysis is based on the integrated luminosity of about 100 pb
−1
collected in 2011, 2012 and 2017.
Existing Monte-Carlo generators with radiative corrections to the
e
+
e
-
→π
+
π
-
process are usually developed under the assumption that pions can be treated as pointlike particles. We study the
e
...+
e
-
→π
+
π
-
γ
process with final-state radiation and test this assumption using simulated events from the MCGPJ generator based on the scalar QED hypothesis. In order to increase a fraction of events with FSR, the analysis was performed in the energy region to the left from the
ρ
-meson peak (660÷785 MeV) that is based on the integrated luminosity of about 8.4 pb
-1
. The experimental data for the photon energy spectrum agree with the simulation results at 1% level.
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