The mass of the
boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. The Higgs boson was the last ...missing component of the model. After observation of the Higgs boson, a measurement of the
boson mass provides a stringent test of the model. We measure the
boson mass,
, using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at a 1.96 tera-electron volt center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. A sample of approximately 4 million
boson candidates is used to obtain
, the precision of which exceeds that of all previous measurements combined (stat, statistical uncertainty; syst, systematic uncertainty; MeV, mega-electron volts;
, speed of light in a vacuum). This measurement is in significant tension with the standard model expectation.
The study of the spin-parity and tensor structure of the interactions of the recently discovered Higgs boson is performed using the H to ZZ, Z gamma*, gamma* gamma* to 4 l, H to WW to l nu l nu, and ...H to gamma gamma decay modes. The full dataset recorded by the CMS experiment during the LHC Run 1 is used, corresponding to an integrated luminosity of up to 5.1 inverse femtobarns at a center-of-mass energy of 7 TeV and up to 19.7 inverse femtobarns at 8 TeV. A wide range of spin-two models is excluded at a 99% confidence level or higher, or at a 99.87% confidence level for the minimal gravity-like couplings, regardless of whether assumptions are made on the production mechanism. Any mixed-parity spin-one state is excluded in the ZZ and WW modes at a greater than 99.999% confidence level. Under the hypothesis that the resonance is a spin-zero boson, the tensor structure of the interactions of the Higgs boson with two vector bosons ZZ, Z gamma, gamma gamma, and WW is investigated and limits on eleven anomalous contributions are set. Tighter constraints on anomalous HVV interactions are obtained by combining the HZZ and HWW measurements. All observations are consistent with the expectations for the standard model Higgs boson with the quantum numbers JPC=0++.
Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing a jet and an imbalance in transverse momentum. The data were collected by ...the CMS detector in proton–proton collisions at the LHC and correspond to an integrated luminosity of 19.7
fb
-1
at a centre-of-mass energy of 8
TeV
. The number of observed events is found to be consistent with the standard model prediction. Limits are placed on the DM-nucleon scattering cross section as a function of the DM particle mass for spin-dependent and spin-independent interactions. Limits are also placed on the scale parameter
M
D
in the Arkani-Hamed, Dimopoulos, and Dvali (ADD) model of large extra dimensions, and on the unparticle model parameter
Λ
U
. The constraints on ADD models and unparticles are the most stringent limits in this channel and those on the DM-nucleon scattering cross section are an improvement over previous collider results.
Combined results are reported from searches for the standard model Higgs boson in proton–proton collisions at s=7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson ...mass range is 110–600 GeV. The analysed data correspond to an integrated luminosity of 4.6–4.8 fb−1. The expected excluded mass range in the absence of the standard model Higgs boson is 118–543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127–600 GeV at 95% CL, and in the mass range 129–525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance ⩾3.1σ anywhere in the search range 110–600 (110–145) GeV is estimated to be 1.5σ(2.1σ). More data are required to ascertain the origin of the observed excess.
A
bstract
A search for a charged Higgs boson is performed with a data sample corresponding to an integrated luminosity of 19.7 ± 0.5 fb
−1
collected with the CMS detector in proton-proton collisions ...at
s
=
8
,TeV. The charged Higgs boson is searched for in top quark decays for
m
H
± <
m
t
−
m
b
, and in the direct production pp → t(b)H
±
for
m
H
± >
m
t
−
m
b
. The H
±
→
τ
±
ν
τ
and H
±
→ tb decay modes in the final states
τ
h
+jets,
μτ
h
,
ℓ
+jets, and
ℓℓ
’ (
ℓ
=e,
μ
) are considered in the search. No signal is observed and 95% confidence level upper limits are set on the charged Higgs boson production. A model-independent upper limit on the product branching fraction
ℬ
t
→
H
±
b
ℬ
H
±
→
τ
±
ν
τ
=
1.2
−
0.15
%
is obtained in the mass range
m
H
± = 80–160 GeV, while the upper limit on the cross section times branching fraction
σ
pp
→
t
b
H
±
ℬ
H
±
→
τ
±
ν
τ
=
0.38
−
0.025
pb is set in the mass range
m
H
+ = 180–600 GeV. Here,
σ
(pp → t(b)H
±
) stands for the cross section sum
σ
pp
→
t
¯
b
H
+
+
σ
pp
→
t
b
¯
H
−
. Assuming
ℬ
H
±
→
t
b
=
1
, an upper limit on
σ
(pp → t(b)H
±
) of 2.0–0.13 pb is set for
m
H
± = 180–600 GeV. The combination of all considered decay modes and final states is used to set exclusion limits in the
m
H
±−tan
β
parameter space in different MSSM benchmark scenarios.
The CDF plug upgrade electromagnetic calorimeter: test beam results Albrow, M.; Aota, S.; Apollinari, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2002, Letnik:
480, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The CDF Plug Upgrade calorimeter, which fully exploits the tile–fiber technique, was tested at the Fermilab meson beamline. The calorimeter was exposed to positron, positively charged pion and ...positive muon beams with energies in the range of 5–
230
GeV
. The energy resolution of the electromagnetic calorimeter to the positron beam is consistent with the design value of
16%/
E
⊕1%
, where E is the energy in units of GeV and ⊕ represents sum in quadrature. The non-linearity for positrons is studied in an energy range of 11–
181
GeV
. It is important to incorporate the response of the preshower detector, the first layer of the electromagnetic calorimeter which is readout separately, into that of the calorimeter to reduce the non-linearity to 1% or less. The energy scale is about
1.46
pC/
GeV
with HAMAMATSU R4125 operated typically at a gain of 2.5×10
4. The response non-uniformity over the surface of a tower of the electromagnetic calorimeter is found to be about 2% with
57
GeV
positrons. Studies of several detailed detector characteristics are also presented.
A peaking structure in the J/ψϕ mass spectrum near threshold is observed in B±→J/ψϕK± decays, produced in pp collisions at s=7 TeV collected with the CMS detector at the LHC. The data sample, ...selected on the basis of the dimuon decay mode of the J/ψ, corresponds to an integrated luminosity of 5.2 fb−1. Fitting the structure to an S-wave relativistic Breit–Wigner lineshape above a three-body phase-space nonresonant component gives a signal statistical significance exceeding five standard deviations. The fitted mass and width values are m=4148.0±2.4(stat.)±6.3(syst.)MeV and Γ=28−11+15(stat.)±19(syst.)MeV, respectively. Evidence for an additional peaking structure at higher J/ψϕ mass is also reported.
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