We report on a set of measurements made on (scintillating) cerium-doped fused-silica fibers using high-energy particle beams. These fibers were uniformly embedded in a copper absorber in order to ...utilize electromagnetic showers as a source of charged particles for generating signals. This new type of cerium-doped fiber potentially offers myriad new applications in calorimeters in high-energy physics, tracking systems, and beam monitoring detectors for future applications. The light yield, pulse shape, attenuation length, and light propagation speeds are given and discussed. Possible future applications are also explored.
DSB:Ce3+ scintillation glass for future Auffray, E; Akchurin, N; Benaglia, A ...
Journal of physics. Conference series,
02/2015, Letnik:
587, Številka:
1
Journal Article
Recenzirano
Odprti dostop
One of the main challenges for detectors at future high-energy collider experiments is the high precision measurement of hadron and jet energy and momentum. One possibility to achieve this is the ...dual-readout technique, which allows recording simultaneously scintillation and Cherenkov light in an active medium in order to extract the electromagnetic fraction of the total shower energy on an event- by-event basis. Making use of this approach in the high luminosity LHC, however, puts stringent requirements on the active materials in terms of radiation hardness. Consequently, the R&D carried out on suitable scintillating materials focuses on the detector performance as well as on radiation tolerance. Among the different scintillating materials under study, scintillating glasses can be a suitable solution due to their relatively simple and cost effective production. Recently a new type of inorganic scintillating glass: Cerium doped DSB has been developed by Radiation Instruments and New Components LLC in Minsk for oil logging industry. This material can be produced either in form of bulk or fiber shape with diameter 0.3-2mm and length up to 2000 mm. It is obtained by standard glass production technology at temperature 1400°C with successive thermal annealing treatment at relatively low temperature. The production of large quantities is relatively easy and the production costs are significantly lower compared to crystal fibers. Therefore, this material is considered as an alternative and complementary solution to crystal fibers in view of a production at industrial scale, as required for a large dual readout calorimeter. In this paper, the first results on optical, scintillation properties as well as the radiation damage behaviour obtained on different samples made with different raw materials and various cerium concentrations will be presented.
Combined measurements of the production and decay rates of the Higgs boson, as well as its couplings to vector bosons and fermions, are presented. The analysis uses the LHC proton–proton collision ...data set recorded with the CMS detector in 2016 at
s
=
13
Te
, corresponding to an integrated luminosity of 35.9
fb
-
1
. The combination is based on analyses targeting the five main Higgs boson production mechanisms (gluon fusion, vector boson fusion, and associated production with a
W
or
Z
boson, or a top quark-antiquark pair) and the following decay modes:
H
→
γ
γ
,
Z
Z
,
W
W
,
τ
τ
,
b
b
, and
μ
μ
. Searches for invisible Higgs boson decays are also considered. The best-fit ratio of the signal yield to the standard model expectation is measured to be
μ
=
1.17
±
0.10
, assuming a Higgs boson mass of
125.09
Ge
. Additional results are given for various assumptions on the scaling behavior of the production and decay modes, including generic parametrizations based on ratios of cross sections and branching fractions or couplings. The results are compatible with the standard model predictions in all parametrizations considered. In addition, constraints are placed on various two Higgs doublet models.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
Combined ATLAS and CMS measurements of the Higgs boson production and decay rates, as well as constraints on its couplings to vector bosons and fermions, are presented. The combination is ...based on the analysis of five production processes, namely gluon fusion, vector boson fusion, and associated production with a
W
or a
Z
boson or a pair of top quarks, and of the six decay modes
H
→
ZZ, W W
, γγ
, ττ, bb
, and
μμ
. All results are reported assuming a value of 125
.
09 GeV for the Higgs boson mass, the result of the combined measurement by the ATLAS and CMS experiments. The analysis uses the CERN LHC proton-proton collision data recorded by the ATLAS and CMS experiments in 2011 and 2012, corresponding to integrated luminosities per experiment of approximately 5 fb
−1
at
s
=
7
TeV and 20 fb
−1
at
s
=
8
TeV. The Higgs boson production and decay rates measured by the two experiments are combined within the context of three generic parameterisations: two based on cross sections and branching fractions, and one on ratios of coupling modifiers. Several interpretations of the measurements with more model-dependent parameterisations are also given. The combined signal yield relative to the Standard Model prediction is measured to be 1
.
09 ± 0
.
11. The combined measurements lead to observed significances for the vector boson fusion production process and for the
H
→
ττ
decay of 5
.
4 and 5
.
5 standard deviations, respectively. The data are consistent with the Standard Model predictions for all parameterisations considered.
A search for invisible decays of a Higgs boson is performed using proton-proton collision data collected with the CMS detector at the LHC in 2016 at a center-of-mass energy s=13TeV, corresponding to ...an integrated luminosity of 35.9fb−1. The search targets the production of a Higgs boson via vector boson fusion. The data are found to be in agreement with the background contributions from standard model processes. An observed (expected) upper limit of 0.33(0.25), at 95% confidence level, is placed on the branching fraction of the Higgs boson decay to invisible particles, assuming standard model production rates and a Higgs boson mass of 125.09 GeV. Results from a combination of this analysis and other direct searches for invisible decays of the Higgs boson, performed using data collected at s=7, 8, and 13 TeV, are presented. An observed (expected) upper limit of 0.19(0.15), at 95% confidence level, is set on the branching fraction of invisible decays of the Higgs boson. The combined limit represents the most stringent bound on the invisible branching fraction of the Higgs boson reported to date. This result is also interpreted in the context of Higgs-portal dark matter models, in which upper bounds are placed on the spin-independent dark-matter-nucleon scattering cross section.
A search for narrow, low-mass, scalar, and pseudoscalar resonances decaying to bottom quark-antiquark pairs is presented. The search is based on events recorded in √ s = 13 TeV proton-proton ...collisions with the CMS detector at the LHC, collected in 2016, and corresponding to an integrated luminosity of 35.9 fb−1 . The search selects events in which the resonance would be produced with high transverse momentum because of the presence of initial- or final-state radiation. In such events, the decay products of the resonance would be reconstructed as a single large-radius jet with high mass and two-prong substructure. A potential signal would be identified as a narrow excess in the jet invariant mass spectrum. No evidence for such a resonance is observed within the mass range from 50 to 350 GeV, and upper limits at 95% confidence level are set on the product of the cross section and branching fraction to a bottom quark-antiquark pair. These constitute the first constraints from the LHC on exotic bottom quark-antiquark resonances with masses below 325 GeV.
Measurements of two- and multi-particle angular correlations in pp collisions at s=5,7, and 13TeV are presented as a function of charged-particle multiplicity. The data, corresponding to integrated ...luminosities of 1.0pb−1 (5 TeV), 6.2pb−1 (7 TeV), and 0.7pb−1 (13 TeV), were collected using the CMS detector at the LHC. The second-order (v2) and third-order (v3) azimuthal anisotropy harmonics of unidentified charged particles, as well as v2 of KS0 and Λ/Λ‾ particles, are extracted from long-range two-particle correlations as functions of particle multiplicity and transverse momentum. For high-multiplicity pp events, a mass ordering is observed for the v2 values of charged hadrons (mostly pions), KS0, and Λ/Λ‾, with lighter particle species exhibiting a stronger azimuthal anisotropy signal below pT≈2GeV/c. For 13 TeV data, the v2 signals are also extracted from four- and six-particle correlations for the first time in pp collisions, with comparable magnitude to those from two-particle correlations. These observations are similar to those seen in pPb and PbPb collisions, and support the interpretation of a collective origin for the observed long-range correlations in high-multiplicity pp collisions.
A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H arrow right gamma gamma and H arrow right ZZ arrow ...right 4scriptl decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09+ or -0.21 (stat)+ or -0.11 (syst) GeV.
Observation of t t ¯ H Production Erö, J.; Flechl, M.; Schieck, J. ...
Physical review letters,
06/2018, Letnik:
120, Številka:
23
Journal Article
Recenzirano
Odprti dostop
Here, the observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of ...√s=7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9 fb-1, respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is1.26+0.31–0.26.
Evidence for the light-by-light scattering process, γγ→γγ, in ultraperipheral PbPb collisions at a centre-of-mass energy per nucleon pair of 5.02TeV is reported. The analysis is conducted using a ...data sample corresponding to an integrated luminosity of 390μb−1 recorded by the CMS experiment at the LHC. Light-by-light scattering processes are selected in events with two photons exclusively produced, each with transverse energy ETγ>2GeV, pseudorapidity |ηγ|<2.4, diphoton invariant mass mγγ>5GeV, diphoton transverse momentum pTγγ<1GeV, and diphoton acoplanarity below 0.01. After all selection criteria are applied, 14 events are observed, compared to expectations of 9.0±0.9(theo) events for the signal and 4.0±1.2(stat) for the background processes. The excess observed in data relative to the background-only expectation corresponds to a significance of 3.7 standard deviations, and has properties consistent with those expected for the light-by-light scattering signal. The measured fiducial light-by-light scattering cross section, σfid(γγ→γγ)=120±46(stat)±28(syst)±12(theo)nb, is consistent with the standard model prediction. The mγγ distribution is used to set new exclusion limits on the production of pseudoscalar axion-like particles, via the ▪ process, in the mass range ▪.