The proposed International Linear Collider (ILC) is well-suited for discovering physics beyond the Standard Model and for precisely unraveling the structure of the underlying physics. The physics ...return can be maximized by the use of polarized beams. This report shows the paramount role of polarized beams and summarizes the benefits obtained from polarizing the positron beam, as well as the electron beam. The physics case for this option is illustrated explicitly by analyzing reference reactions in different physics scenarios. The results show that positron polarization, combined with the clean experimental environment provided by the linear collider, allows to improve strongly the potential of searches for new particles and the identification of their dynamics, which opens the road to resolve shortcomings of the Standard Model. The report also presents an overview of possible designs for polarizing both beams at the ILC, as well as for measuring their polarization.
The ”Snowmass Points and Slopes” (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present ...and future experiments. This set of benchmarks was agreed upon at the 2001 ”Snowmass Workshop on the Future of Particle Physics” as a consensus based on different existing proposals.
New sets of parameters (“tunes”) for the underlying-event (UE) modelling of the
pythia
8,
pythia6
and
herwig++
Monte Carlo event generators are constructed using different parton distribution ...functions. Combined fits to CMS UE proton–proton (
p
p
) data at
s
=
7
TeV
and to UE proton–antiproton (
p
p
¯
) data from the CDF experiment at lower
s
, are used to study the UE models and constrain their parameters, providing thereby improved predictions for proton–proton collisions at 13
TeV
. In addition, it is investigated whether the values of the parameters obtained from fits to UE observables are consistent with the values determined from fitting observables sensitive to double-parton scattering processes. Finally, comparisons are presented of the UE tunes to “minimum bias” (MB) events, multijet, and Drell–Yan (
q
q
¯
→
Z
/
γ
∗
→
lepton-antilepton+jets) observables at 7 and 8
TeV
, as well as predictions for MB and UE observables at 13
TeV
.
Properties of the Higgs boson with mass near 125 GeV are measured in proton-proton collisions with the CMS experiment at the LHC. Comprehensive sets of production and decay measurements are combined. ...The decay channels include gammagamma, ZZ, WW, tautau, bb, and mumu pairs. The data samples were collected in 2011 and 2012 and correspond to integrated luminosities of up to 5.1fb^-1 at 7 TeV and up to 19.7 fb^-1 at 8 TeV. From the high-resolution gammagamma and ZZ channels, the mass of the Higgs boson is determined to be 125.02^+0.26_-0.27(stat)^+0.14_-0.15(syst)GeV. For this mass value, the event yields obtained in the different analyses tagging specific decay channels and production mechanisms are consistent with those expected for the standard model Higgs boson. The combined best-fit signal relative to the standard model expectation is 1.00 +/- 0.09(stat)^+0.08_-0.07(theo) +/- 0.07(syst) at the measured mass. The couplings of the Higgs boson are probed for deviations in magnitude from the standard model predictions in multiple ways, including searches for invisible and undetected decays. No significant deviations are found.
The Physics of the B Factories Bevan, Adrian; Golob, Bostjan; Mannel, Thomas ...
The European physical journal. C, Particles and fields,
March 2015, Letnik:
74, Številka:
11
eBook, Journal Article
Recenzirano
Odprti dostop
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related ...issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.
The second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in p-Pb and PbPb collisions over a wide pseudorapidity (η) range based on correlations among six or more charged particles. ...The p-Pb data, corresponding to an integrated luminosity of 35 nb-1, were collected during the 2013 LHC p-Pb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semiperipheral PbPb collision data at √sNN=2.76 TeV, corresponding to an integrated luminosity of 2.5 μb-1 and covering a similar range of particle multiplicities as the p-Pb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the p-Pb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large Δη) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a p-Pb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multiparticle dynamics of collision systems with a very small overlapping region.
Observation of the diphoton decay mode of the recently discovered Higgs boson and measurement of some of its properties are reported. The analysis uses the entire dataset collected by the CMS ...experiment in proton-proton collisions during the 2011 and 2012 LHC running periods. The data samples correspond to integrated luminosities of 5.1
fb
-1
at
s
=
7
TeV
and 19.7
fb
-1
at 8
TeV
. A clear signal is observed in the diphoton channel at a mass close to 125
GeV
with a local significance of
5.7
σ
, where a significance of
5.2
σ
is expected for the standard model Higgs boson. The mass is measured to be
124.70
±
0.34
GeV
=
124.70
±
0.31
(stat)
±
0.15
(syst)
GeV
, and the best-fit signal strength relative to the standard model prediction is
1
.
14
-
0.23
+
0.26
=
1.14
±
0.21
(stat)
-
0.05
+
0.09
(syst)
-
0.09
+
0.13
(theo)
. Additional measurements include the signal strength modifiers associated with different production mechanisms, and hypothesis tests between spin-0 and spin-2 models.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Searches for the direct electroweak production of supersymmetric charginos, neutralinos, and sleptons in a variety of signatures with leptons and
W
,
Z
, and Higgs bosons are presented. Results are ...based on a sample of proton-proton collision data collected at center-of-mass energy
s
=
8
TeV
with the CMS detector in 2012, corresponding to an integrated luminosity of 19.5
fb
-1
. The observed event rates are in agreement with expectations from the standard model. These results probe charginos and neutralinos with masses up to 720
GeV
, and sleptons up to 260
GeV
, depending on the model details.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A study of vector boson scattering in pp collisions at a center-of-mass energy of 8 TeV is presented. The data sample corresponds to an integrated luminosity of 19.4 fb(-1) collected with the CMS ...detector. Candidate events are selected with exactly two leptons of the same charge, two jets with large rapidity separation and high dijet mass, and moderate missing transverse energy. The signal region is expected to be dominated by electroweak same-sign W-boson pair production. The observation agrees with the standard model prediction. The observed significance is 2.0 standard deviations, where a significance of 3.1 standard deviations is expected based on the standard model. Cross section measurements for W(±)W(±) and WZ processes in the fiducial region are reported. Bounds on the structure of quartic vector-boson interactions are given in the framework of dimension-eight effective field theory operators, as well as limits on the production of doubly charged Higgs bosons.
Results on two-particle angular correlations for charged particles emitted in proton-proton collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV are presented, using data collected with the ...CMS detector over a broad range of pseudorapidity (
η
) and azimuthal angle (
ϕ
). Short-range correlations in Δ
η
, which are studied in minimum bias events, are characterized using a simple “independent cluster” parametrization in order to quantify their strength (cluster size) and their extent in
η
(cluster decay width). Long-range azimuthal correlations are studied differentially as a function of charged particle multiplicity and particle transverse momentum using a 980 nb
−1
data set at 7 TeV. In high multiplicity events, a pronounced structure emerges in the two-dimensional correlation function for particle pairs with intermediate
p
T
of 1–3 GeV/
c
, 2.0 < |Δ
η
| < 4
.
8 and Δ
ϕ
≈ 0. This is the first observation of such a long-range, near-side feature in two-particle correlation functions in
pp
or
collisions.
PDF
