Abstract
The PADME experiment at LNF-INFN employs positron-on-target-annihilation
to search for new light particles. Crucial parts of the experiment are the charged
particle detectors, composed of ...plastic scintillator bars with light transmitted
by wavelength shifting fibers to silicon photomultipliers (SiPMs). The location of
the detector — close to a turbomolecular pump, inside a vacuum tank, and exposed
to 0.5 T magnetic field — has driven the design of custom modular SiPM front-end
and power supply electronics. The design of the system and its performance, confirming
the desired sub-ns resolution on the reconstructed particle flying times, is shown
and discussed.
Abstract
During 2022 data taking (Run III) PADME searched for a resonant production and a visible decay of the X17 particle into e
+
e
-
. A precise knowledge within 1% uncertainty of the number of ...positrons was required for the observation. To that purpose, an array of 2 × 6 Timepix3 (total of 512 × 1536 pixels) hybrid pixel detectors operated in data-streaming mode with ToA resolution of 1.56 ns for every pixel was employed. Two methods for data acquisition were developed. A frame-based method, integrating the number of hits for each individual pixel for a predefined period of time served for monitoring the beam conditions and to provide a rough estimation of the beam distribution and number of positrons. A data streaming mode exploiting the nanosecond time resolution of Timepix3 detector was used for precise characterization of the transverse beam profile and the distribution of the incident positrons within each bunch of ∼ 200 ns duration.
The PADME beam line Monte Carlo simulation Bossi, F.; Branchini, P.; Buonomo, B. ...
The journal of high energy physics,
09/2022, Letnik:
2022, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A
bstract
The PADME experiment at the DAΦNE Beam-Test Facility (BTF) of the INFN Laboratory of Frascati is designed to search for invisible decays of dark sector particles produced in ...electron-positron annihilation events with a positron beam and a thin fixed target, by measuring the missing mass of single-photon final states. The presence of backgrounds originating from beam halo particles can significantly reduce the sensitivity of the experiment. To thoroughly understand the origin of the beam background contribution, a detailed G
eant
4-based Monte Carlo simulation has been developed, containing a full description of the detector together with the beam line and its optical elements. This simulation allows the full interactions of each particle to be described, both during beam line transport and during detection, a possibility which represents an innovative way to obtain reliable background predictions.
In July 2012, the ATLAS and CMS collaborations at the CERN Large Hadron Collider announced the observation of a Higgs boson at a mass of around 125 gigaelectronvolts. Ten years later, and with the ...data corresponding to the production of a 30-times larger number of Higgs bosons, we have learnt much more about the properties of the Higgs boson. The CMS experiment has observed the Higgs boson in numerous fermionic and bosonic decay channels, established its spin-parity quantum numbers, determined its mass and measured its production cross-sections in various modes. Here the CMS Collaboration reports the most up-to-date combination of results on the properties of the Higgs boson, including the most stringent limit on the cross-section for the production of a pair of Higgs bosons, on the basis of data from proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts. Within the uncertainties, all these observations are compatible with the predictions of the standard model of elementary particle physics. Much evidence points to the fact that the standard model is a low-energy approximation of a more comprehensive theory. Several of the standard model issues originate in the sector of Higgs boson physics. An order of magnitude larger number of Higgs bosons, expected to be examined over the next 15 years, will help deepen our understanding of this crucial sector.
The PADME experiment at the LNF Beam Test Facility searches for dark photons produced in the annihilation of positrons with the electrons of a fixed target. The strategy is to look for the reaction ...e++e−→γ+A′, where A′ is the dark photon, which cannot be observed directly or via its decay products. The electromagnetic calorimeter plays a key role in the experiment by measuring the energy and position of the final-state γ. The missing four-momentum carried away by the A′ can be evaluated from this information and the particle mass inferred. This paper presents the design, construction, and calibration of the PADME's electromagnetic calorimeter. The results achieved in terms of equalisation, detection efficiency and energy resolution during the first phase of the experiment demonstrate the effectiveness of the various tools used to improve the calorimeter performance with respect to earlier prototypes.
Abstract
The PADME experiment is designed to search for a
hypothetical dark photon
A
'
produced in positron-electron
annihilation using a bunched positron beam at the Beam Test Facility
of the INFN ...Laboratori Nazionali di Frascati. The expected
sensitivity to the
A
'
-photon mixing parameter
ϵ
is 10
-3
, for
A
'
mass ≤ 23.5 MeV/
c
2
after
collecting ∼ 10
13
positrons-on-target.
This paper presents the PADME detector status after commissioning in
July 2019. In addition, the software algorithms employed to
reconstruct physics objects, such as photons and charged particles,
and the calibration procedures adopted are illustrated in detail.
The results show that the experimental apparatus reaches the design
performance, and is able to identify and measure standard
electromagnetic processes, such as positron bremsstrahlung and
electron-positron annihilation into two photons.
•For the first time, an LC-ESI-MS/MS method is reported for captan, captafol, folpet & iprodione.•The scope of the method also includes degradation products of captan and folpet.•Samples were ...cryogenically comminuted & extracted with acidified ethyl acetate or acetonitrile.•Limits of quantification were ≤0.01 mg/kg for all these pesticides in fruits and vegetables.•This method provides a viable alternative to conventional GC–MS/MS methods with improved precision & accuracy.
An improved liquid chromatography tandem mass spectrometry method is reported for the determination of residues of captan (+tetrahydrophthalimide), captafol, folpet (+phthalimide), and iprodione in fruits and vegetables. The optimized electrospray ionization parameters (high cone gas flow, and a low desolvation temperature) did not result in degradation of target compounds, rather they provided a significant advantage over the conventional GC–MS/MS methods, which lack sensitivity and repeatability. Strategies for minimizing losses in recovery of these compounds during sample preparation included cryogenic comminution, extraction with acidified ethyl acetate or acetonitrile, and dilution of the final extract with acidified water prior to LC-MS/MS analysis. The method performance complied with the SANTE/11813/2017 guidelines, with recoveries in the range of 70–120% at the LOQ of 0.01 mg/kg across the tested matrices at various pHs. The efficiency of the method was reflected in its precision (RSDs < 10%) for incurred residues.
A large sample of cosmic ray events collected by the CMS detector is exploited to measure the specific energy loss of muons in the lead tungstate of the electromagnetic calorimeter. The measurement ...spans a momentum range from 5 GeV/c to 1 TeV/c. The results are consistent with the expectations over the entire range. The calorimeter energy scale, set with 120 GeV/c electrons, is validated down to the sub-GeV region using energy deposits, of order 100 MeV, associated with low-momentum muons. The muon critical energy in lead tungstate is measured to be 160+5/-6 plus or minus 8 GeV, in agreement with expectations. This is the first experimental determination of muon critical energy.
In minute virus of mice (MVM) capsids, icosahedral five-fold channels serve as portals mediating genome packaging, genome release, and the phased extrusion of viral peptides. Previous studies suggest ...that residues L172 and V40 are essential for channel function. The structures of MVMi wildtype, and mutant L172T and V40A virus-like particles (VLPs) were solved from cryo-EM data. Two constriction points, termed the mid-gate and inner-gate, were observed in the channels of wildtype particles, involving residues L172 and V40 respectively. While the mid-gate of V40A VLPs appeared normal, in L172T adjacent channel walls were altered, and in both mutants there was major disruption of the inner-gate, demonstrating that direct L172:V40 bonding is essential for its structural integrity. In wildtype particles, residues from the N-termini of VP2 map into claw-like densities positioned below the channel opening, which become disordered in the mutants, implicating both L172 and V40 in the organization of VP2 N-termini.
•Parvovirus VP2 N-terminal density mapped to the five fold pore.•Seven previously disordered residues of were resolved.•Differences between wild-type and mutant viruses mapped to the base of the pore.•Conformation linked to virus function published by Cotmore and Tattersall (2012).
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