560 research outputs found
Inclusive Jets in PHP
Differential inclusive-jet cross sections have been measured in
photoproduction for boson virtualities Q^2 < 1 GeV^2 with the ZEUS detector at
HERA using an integrated luminosity of 300 pb^-1. Jets were identified in the
laboratory frame using the k_T, anti-k_T or SIScone jet algorithms. Cross
sections are presented as functions of the jet pseudorapidity, eta(jet), and
the jet transverse energy, E_T(jet). Next-to-leading-order QCD calculations
give a good description of the measurements, except for jets with low E_T(jet)
and high eta(jet). The cross sections have the potential to improve the
determination of the PDFs in future QCD fits. Values of alpha_s(M_Z) have been
extracted from the measurements based on different jet algorithms. In addition,
the energy-scale dependence of the strong coupling was determined.Comment: To appear in the proceedings of the EPS HEP 2013 conferenc
Double Higgs boson production and Higgs self-coupling extraction at CLIC
AbstractThe Compact Linear Collider (CLIC) is a future electronâpositron collider that will allow measurements of the trilinear Higgs self-coupling in double Higgs boson events produced at its high-energy stages with collision energies from
s
 = 1.4 to 3 TeV. The sensitivity to the Higgs self-coupling is driven by the measurements of the cross section and the invariant mass distribution of the Higgs-boson pair in the W-boson fusion process,
e
+
e
-
â
HH
Μ
Μ
ÂŻ
. It is enhanced by including the cross-section measurement of ZHHÂ production at 1.4Â TeV. The expected sensitivity of CLIC for Higgs pair production through W-boson fusion is studied for the decay channels
b
b
ÂŻ
b
b
ÂŻ
 and
b
b
ÂŻ
W
W
â
 using full detector simulation including all relevant backgrounds at
s
= 1.4Â TeV with an integrated luminosity of
L
 = 2.5 ab
-
1
and at
s
= 3Â TeV with
L
 = 5 ab
-
1
. Combining
e
+
e
-
â
HH
Μ
Μ
ÂŻ
and ZHHÂ cross-section measurements at 1.4Â TeV with differential measurements in
e
+
e
-
â
HH
Μ
Μ
ÂŻ
events at 3Â TeV, CLIC will be able to measure the trilinear Higgs self-coupling with a relative uncertainty of
-
8
%
and
+
11
%
at 68% C.L., assuming the Standard Model. In addition, prospects for simultaneous constraints on the trilinear Higgs self-coupling and the Higgs-gauge coupling HHWW are derived based on the
HH
Μ
Μ
ÂŻ
measurement.</jats:p
Measurement of Ï(HVeVe) x BR(Hâ ZZ*) and Higgs production in ZZ fusion at a 1.4 TeV CLIC collider
This paper presents the potential measurement at 1.4 TeV CLIC of the cross-section (times branching ratio) of the Higgs production via WW fusion with the Higgs subsequently decaying in ZZâ€, s(HnenÂŻe)â„BR(H ! ZZâ€), and of the Higgs production via ZZ fusion with the Higgs subsequently decaying in bbÂŻ, s(He+e)â„BR(H ! bbÂŻ). For the H ! ZZ†decay the hadronic final state, ZZ†! qqqÂŻ qÂŻ, and the semi-leptonic final state, ZZ†! qqlÂŻ +l , are considered. The results show that s(HnenÂŻe)â„BR(H ! ZZâ€) can be measured with a precision of 18.3% and 6% for the hadronic and semi-leptonic channel, respectively. s(He+e)â„BR(H ! bbÂŻ) can be measured with a precision of 1.7%. This measurement also contributes to the determination of the Higgs coupling to the Z boson, gHZZInternational Workshop on Future Linear Colliders (LCWS14) : October 6-10, Belgrade, 2014
Performance of a spaghetti calorimeter prototype with tungsten absorber and garnet crystal fibres
A spaghetti calorimeter (SPACAL) prototype with scintillating crystal fibres
was assembled and tested with electron beams of energy from 1 to 5 GeV. The
prototype comprised radiation-hard Cerium-doped GdAlGaO
(GAGG:Ce) and YAlO (YAG:Ce) embedded in a pure tungsten
absorber. The energy resolution was studied as a function of the incidence
angle of the beam and found to be of the order of ,
in line with the LHCb Shashlik technology. The time resolution was measured
with metal channel dynodes photomultipliers placed in contact with the fibres
or coupled via a light guide, additionally testing an optical tape to glue the
components. Time resolution of a few tens of picosecond was achieved for all
the energies reaching down to (18.5 0.2) ps at 5 GeV.Comment: 14 pages, 8 figures, published on NIM
Dimension-6 operator analysis of the CLIC sensitivity to new physics
We estimate the possible accuracies of measurements at the proposed CLICe+ eâ collider of Higgs and W+Wâ production at centre-of-mass energies up to 3 TeV,
incorporating also Higgsstrahlung projections at higher energies that had not been considered previously, and use them to explore the prospective CLIC sensitivities to decoupled new physics. We present the resulting constraints on the Wilson coefficients of dimension6 operators in a model-independent approach based on the Standard Model effective field theory (SM EFT). The higher centre-of-mass energy of CLIC, compared to other projects such as the ILC and CEPC, gives it greater sensitivity to the coefficients of some of the operators we study. We find that CLIC Higgs measurements may be sensitive to new physics scales Î = O(10) TeV for individual operators, reduced to O(1) TeV sensitivity for a global fit marginalising over the coefficients of all contributing operators. We give some examples
of the corresponding prospective constraints on specific scenarios for physics beyond the SM, including stop quarks and the dilaton/radion
Report of the Topical Group on Electroweak Precision Physics and Constraining New Physics for Snowmass 2021
The precise measurement of physics observables and the test of their
consistency within the standard model (SM) are an invaluable approach,
complemented by direct searches for new particles, to determine the existence
of physics beyond the standard model (BSM). Studies of massive electroweak
gauge bosons (W and Z bosons) are a promising target for indirect BSM searches,
since the interactions of photons and gluons are strongly constrained by the
unbroken gauge symmetries. They can be divided into two categories: (a) Fermion
scattering processes mediated by s- or t-channel W/Z bosons, also known as
electroweak precision measurements; and (b) multi-boson processes, which
include production of two or more vector bosons in fermion-antifermion
annihilation, as well as vector boson scattering (VBS) processes. The latter
categories can test modifications of gauge-boson self-interactions, and the
sensitivity is typically improved with increased collision energy.
This report evaluates the achievable precision of a range of future
experiments, which depend on the statistics of the collected data sample, the
experimental and theoretical systematic uncertainties, and their correlations.
In addition it presents a combined interpretation of these results, together
with similar studies in the Higgs and top sector, in the Standard Model
effective field theory (SMEFT) framework. This framework provides a
model-independent prescription to put generic constraints on new physics and to
study and combine large sets of experimental observables, assuming that the new
physics scales are significantly higher than the EW scale.Comment: 55 pages; Report of the EF04 topical group for Snowmass 202
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