Accurate measurements of physical processes in high energy frontier experiments demand exceptional spatial, temporal, and energy precision to discern the physics behind high-energy particle jets. ...Calorimeters, like other detection systems, must be able to meet these increasingly challenging performance requirements. In the prospective TeV-scale Muon Collider, the primary hurdle in designing detectors and devising event reconstruction algorithms is the challenge posed by Beam-Induced Background (BIB). Nevertheless, it is conceivable to mitigate the impact of BIB on the Muon Collider's calorimeter by capitalizing on certain characteristics and ensuring key features such as high granularity, precise timing, longitudinal segmentation, and superior energy resolution. This is what the here described Research and Development is trying to achieve with an innovative semi-homogeneous electromagnetic calorimeter constructed from stackable and interchangeable modules composed of lead fluoride crystals (PbF2). These modules are equipped with surface-mount UV-extended Silicon Photomultipliers (SiPMs) and are collectively referred to as the Crilin calorimeter (CRystal calorImeter with Longitudinal INformation). The challenge lies in making sure this calorimeter can operate effectively within an extremely harsh radiation environment, enduring an annual neutron flux of <inline-formula> <tex-math notation="LaTeX">10^{14}~n_{1\text {MeV}}/\text {cm}^{2} </tex-math></inline-formula> and a total ionizing dose (TID) of 10 kGy. In this article, the radiation tolerance measured in several irradiation campaigns is discussed, and the timing performances during a test beam at CERN-H2 with 120-GeV electrons. Additionally, a description of the latest prototype, Proto-1, is provided together with the results of the latest low-energy beam test at the LNF beam test facility (BTF) with 450 MeV electrons.
A
bstract
The quantum interference between the decays of entangled neutral kaons is studied in the process
ϕ
→ K
S
K
L
→
π
+
π
−
π
+
π
−
, which exhibits the characteristic Einstein-Podolsky-Rosen ...correlations that prevent both kaons to decay into
π
+
π
−
at the same time. This constitutes a very powerful tool for testing at the utmost precision the quantum coherence of the entangled kaon pair state, and to search for tiny decoherence and
CPT
violation effects, which may be justified in a quantum gravity framework.
The analysed data sample was collected with the KLOE detector at DAΦNE, the Frascati
ϕ
-factory, and corresponds to an integrated luminosity of about 1.7 fb
−
1
, i.e. to about 1
.
7 × 10
9
ϕ
→ K
S
K
L
decays produced. From the fit of the observed ∆
t
distribution, being ∆
t
the difference of the kaon decay times, the decoherence and
CPT
violation parameters of various phenomenological models are measured with a largely improved accuracy with respect to previous analyses.
The results are consistent with no deviation from quantum mechanics and
CPT
symmetry, while for some parameters the precision reaches the interesting level at which — in the most optimistic scenarios — quantum gravity effects might show up. They provide the most stringent limits up to date on the considered models.
In modern experiment, a high granularity is required in order to distinguish signal particles from background and to solve the substructures necessary for jet identification. Time of arrival ...measurements in the calorimeter could play an important role in HL-LHC, since a high number of pile-up collisions is expected, and the timing could be used to assign clusters to the corresponding interaction vertex. In a Muon Collider, the timing could be used to remove signals produced by beam-induced background, asynchronous with respect to the bunch crossing. The calorimeter energy resolution is also fundamental to measure the kinematic properties of jets: a finely segmented calorimeter design should be favored in order to solve the jet substructure. However, this contrasts with the requirement for high timing resolution even for signal events involving low energy deposits, such as in the case of high impulse muons. Our proposed design, the Crilin calorimeter, is a semi-homogeneous calorimeter based on Lead Fluoride (PbF
2
) Crystals readout by surface-mount UV-extended Silicon Photomultipliers (SiPMs). In this paper, the development of a small prototype consisting of 2 layers of 3 × 3 crystals each is reported along with the relative results.
Abstract
The use of Silicon Photo-Multipliers (SiPMs) has become popular in the
design of High Energy Physics experimental apparatus with a growing
interest for their application in detector area ...where a significant
amount of non-ionising dose is delivered. For these devices, the main
effect caused by the neutron fluence is a linear increase of the leakage
current. In this paper, we present a technique that provides a
partial recovery of the neutron damage on SiPMs by means of an
Electrical Induced Annealing. Tests were performed, at the temperature of 20°C, on a sample of
three SiPM arrays (2×3) of 6 mm
2
cells with 50 μm
pixel sizes: two from Hamamatsu and one from
SensL. These SiPMs have been exposed to neutrons generated by the Elbe Positron Source facility (Dresden),
up to a total fluence of 8 × 10
11
n
1
MeV-eq
/cm
2
. Our techniques allowed to reduced the leakage
current of a factor ranging between 15-20 depending on the overbias
used and the SiPM vendor. Because, during the process the
SiPM current can reach O(100 mA), the sensors need to be operated in a condition that
provides thermal dissipation. Indeed, caution must be used when applying this kind of
procedures on the SiPMs, because it may damage permanently the devices themself.
A
bstract
The ratio
R
= Γ(
K
S
→ πeν
)
/
Γ(
K
S
→ π
+
π
−
) has been measured with a sample of 300 million
K
S
mesons produced in
ϕ → K
L
K
S
decays recorded by the KLOE experiment at the DAΦNE
e
+
e
...−
collider.
K
S
→ πeν
events are selected by a boosted decision tree built with kinematic variables and time-of-flight measurements. Data control samples of
K
L
→ πeν
decays are used to evaluate signal selection efficiencies. With 49647
±
316 signal events we measure
R
= (1
.
0421
±
0
.
0066
stat
±
0
.
0075
syst
)
×
10
−
3
. The combination with our previous measurement gives
R
= (1
.
0338
±
0
.
0054
stat
±
0
.
0064
syst
)
×
10
−
3
. From this value we derive the branching fraction
B
(
K
S
→ πeν
) = (7
.
153
±
0
.
037
stat
±
0
.
044
syst
)
×
10
−
4
and
f
+
(0)
|V
us
|
= 0
.
2170
±
0
.
009.
Abstract
The measurement of physics processes at new energy frontier
experiments requires excellent spatial, time, and energy resolutions
to resolve the structure of collimated high-energy jets. In a ...future
Muon Collider, the beam-induced backgrounds (BIB) represent the main
challenge in the design of the detectors and of the event
reconstruction algorithms. The technology and the design of the
calorimeters should be chosen to reduce the effect of the BIB, while
keeping good physics performance. Several requirements can be
inferred: i) high granularity to reduce the overlap of BIB particles
in the same calorimeter cell; ii) excellent timing (of the order of
100 ps) to reduce the out-of-time component of the BIB; iii)
longitudinal segmentation to distinguish the signal showers from the
fake showers produced by the BIB; iv) good energy resolution (less
than 10%/
√E
) to obtain good physics performance, as has
been already demonstrated for conceptual particle flow calorimeters.
Our proposal consists of a semi-homogeneous electromagnetic
calorimeter based on lead fluoride crystals (PbF
2
) read out by
surface-mount UV-extended Silicon Photomultipliers (SiPMs): the
Crilin calorimeter. In this paper, the performance of the Crilin
calorimeter in the Muon Collider framework for hadron jets
reconstruction has been analyzed. We report the characterisation of
individual components together with the development of a small-scale
prototype, consisting of 2 layers of 3 × 3 crystals each.
The Mu2e experiment at Fermilab searches for the charged-lepton flavor violating (CLFV) conversion of a negative muon into an electron in the field of an aluminum nucleus, with a distinctive ...signature of a monoenergetic electron of energy slightly below the muon rest mass (104.967 MeV). The Mu2e goal is to improve by four orders of magnitude the search sensitivity with respect to the previous experiments. Any observation of a CLFV signal will be a clear indication of new physics. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter, and an external veto for cosmic rays surrounding the solenoid. The calorimeter plays an important role in providing particle identification capabilities, a fast online trigger filter, a seed for track reconstruction while working in vacuum, in the presence of 1-T axial magnetic field and in a harsh radiation environment. The calorimeter requirements are to provide a large acceptance for 100-MeV electrons and reach at these energies: 1) a time resolution better than 0.5 ns; 2) an energy resolution <10%; and 3) a position resolution of 1 cm. The calorimeter design consists of two disks, each one made of 674-undoped cesium iodine crystals read by two large area arrays of UV-extended silicon photomultipliers (SiPMs). We report here the construction and the test of the Module-0 prototype. The Module-0 has been exposed to an electron beam in the energy range around 100 MeV at the Beam Test Facility in Frascati. Preliminary results of timing and energy resolution at normal incidence are shown. A discussion of the technical aspects of the calorimeter engineering is also reported in this paper.
Abstract
Lead fluoride (PbF
2
) crystals represent an excellent and
relatively innovative choice for high resolution electromagnetic
calorimeters with high granularity and fast timing for high
...intensity environments. For this reason two PbF
2
crystals, sized
5× 5 × 40 mm
3
, were irradiated with
60
Co
photons up to ∼ 4 Mrad and with 14 MeV neutrons up to a
10
13
n/cm
2
total fluence. Their loss in transmittance was
evaluated at different steps of the photon and neutron irradiation
campaign, resulting in a total of 30% loss above 350 nm. With
crystals always kept in dark conditions, natural and thermal
annealing, as well as optical bleaching with 400 nm light, were
performed on the irradiated specimens, resulting in a partial
recovery of their original optical characteristics.
The Mu2e experiment is constructing a calorimeter consisting of 1348 undoped cesium iodide (CsI) crystals in two disks. Each crystal has a dimension of 34 × 34 × 200 mm3 and is readout by a ...large-area silicon photomultipliers array. A series of technical specifications on mechanical and optical parameters was defined according to the calorimeter physics requirements. Preproduction CsI crystals were procured from three firms: Amcrys, Saint-Gobain, and Shanghai Institute of Ceramics. We report the quality assurance on crystal's scintillation properties and their radiation hardness against ionization dose and neutrons. With a fast decay time of about 30 ns and a light output of more than 100 p.e./MeV measured by a bialkali photomultiplier tube, undoped CsI crystals provide a cost-effective solution for Mu2e.
Crilin (Crystal Calorimeter with Longitudinal Information) is a semi-homogeneous, longitudinally segmented electromagnetic calorimeter based on high-
Z
, ultra-fast crystals with UV-extended SiPM ...readout. The Crilin design has been proposed as a candidate solution for both a future Muon Collider barrel ECAL and for the Small Angle Calorimeter of the HIKE experiment. As a part of the Crilin development program, we have carried out beam tests of small (10 × 10 × 40 mm
3
) lead fluoride (PbF
2
) and ultra-fast lead tungstate (PbWO
4
, PWO-UF) crystals with 120 GeV electrons at the CERN SPS to study the light yield, timing response, and systematics of light collection with a proposed readout scheme. For a single crystal of PbF
2
, corresponding to a single Crilin cell, a time resolution of better than 25 ps is obtained for
>
3 GeV of deposited energy. For a single cell of PWO-UF, a time resolution of better than 45 ps is obtained for the same range of deposited energy. This timing performance fully satisfies the design requirements for the Muon Collider and HIKE experiments. Further optimizations of the readout scheme and crystal surface preparation are expected to bring further improvements.
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