A
bstract
A combination of measurements sensitive to the
CP
violation angle
γ
of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between
...D
0
and
D
¯
0
mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CERN’s Large Hadron Collider, are combined for the first time. This method provides an improvement on the precision of the charm mixing parameter
y
by a factor of two with respect to the current world average. The charm mixing parameters are determined to be
x
=
0.400
−
0.053
+
0.052
%
and
y
=
0.630
−
0.030
+
0.033
%
. The angle
γ
is found to be
γ
=
65.4
−
4.2
+
3.8
°
and is the most precise determination from a single experiment.
The extraction of the strange quark parton distribution function (PDF) poses a long-standing puzzle. Measurements from neutrino-nucleus deep inelastic scattering (DIS) experiments suggest the strange ...quark is suppressed compared to the light sea quarks, while recent studies of
W
±
/
Z
boson production at the LHC imply a larger strange component at small
x
values. As the parton flavor determination in the proton depends on nuclear corrections, e.g. from heavy-target DIS, LHC heavy ion measurements can provide a distinct perspective to help clarify this situation. In this investigation we extend the nCTEQ15 nPDFs to study the impact of the LHC proton-lead
W
±
/
Z
production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC
W
±
/
Z
proton analyses and the neutrino-nucleus DIS data. We identify these new nPDFs as
nCTEQ15WZ
. Our calculations are performed using a new implementation of the nCTEQ code (
nCTEQ++
) based on C++ which enables us to easily interface to external programs such as HOPPET, APPLgrid and MCFM. Our results indicate that, as suggested by the proton data, the small
x
nuclear strange sea appears larger than previously expected, even when the normalization of the
W
±
/
Z
data is accommodated in the fit. Extending the nCTEQ15 analysis to include LHC
W
±
/
Z
data represents an important step as we advance toward the next generation of nPDFs.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for the Higgs boson decaying into a pair of charm quarks is presented. The analysis uses proton–proton collisions to target the production of a Higgs boson in association with a leptonically ...decaying
W
or
Z
boson. The dataset delivered by the LHC at a centre-of-mass energy of
and recorded by the ATLAS detector corresponds to an integrated luminosity of 139
fb
-
1
. Flavour-tagging algorithms are used to identify jets originating from the hadronisation of charm quarks. The analysis method is validated with the simultaneous measurement of
WW
,
WZ
and
ZZ
production, with observed (expected) significances of 2.6 (2.2) standard deviations above the background-only prediction for the
(
W
/
Z
)
Z
(
→
c
c
¯
)
process and 3.8 (4.6) standard deviations for the
(
W
/
Z
)
W
(
→
c
q
)
process. The
(
W
/
Z
)
H
(
→
c
c
¯
)
search yields an observed (expected) upper limit of 26 (31) times the predicted Standard Model cross-section times branching fraction for a Higgs boson with a mass of
, corresponding to an observed (expected) constraint on the charm Yukawa coupling modifier
|
κ
c
|
<
8.5
(
12.4
)
, at the 95% confidence level. A combination with the ATLAS
(
W
/
Z
)
H
,
H
→
b
b
¯
analysis is performed, allowing the ratio
κ
c
/
κ
b
to be constrained to less than 4.5 at the 95% confidence level, smaller than the ratio of the b- and c-quark masses, and therefore determines the Higgs-charm coupling to be weaker than the Higgs-bottom coupling at the 95% confidence level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Prospects for fundamental physics with LISA Barausse, Enrico; Hertog, Thomas; Hughes, Scott A. ...
General relativity and gravitation,
2020, Letnik:
52, Številka:
8
Journal Article
Recenzirano
Odprti dostop
In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental physics. Given the ...very broad range of topics that might be relevant to LISA,we present here a sample of what we view as particularly promising fundamental physics directions. We organize these directions through a “science-first” approach that allows us to classify how LISA data can inform theoretical physics in a variety of areas. For each of these theoretical physics classes, we identify the sources that are currently expected to provide the principal contribution to our knowledge, and the areas that need further development. The classification presented here should not be thought of as cast in stone, but rather as a fluid framework that is amenable to change with the flow of new insights in theoretical physics.
A
bstract
We calculate coherent elastic neutrino-nucleus scattering cross sections on spin-0 nuclei (e.g.
40
Ar and
28
Si) at energies below 100 MeV within the Standard Model and account for all ...effects of permille size. We provide a complete error budget including uncertainties at nuclear, nucleon, hadronic, and quark levels separately as well as perturbative error. Our calculation starts from the four-fermion effective field theory to explicitly separate heavy-particle mediated corrections (which are absorbed by Wilson coefficients) from light-particle contributions. Electrons and muons running in loops introduce a non- trivial dependence on the momentum transfer due to their relatively light masses. These same loops, and those mediated by tau leptons, break the flavor universality because of mass-dependent electromagnetic radiative corrections. Nuclear physics uncertainties significantly cancel in flavor asymmetries resulting in subpercent relative errors. We find that for low neutrino energies, the cross section can be predicted with a relative precision that is competitive with neutrino-electron scattering. We highlight potentially useful applications of such a precise cross section prediction ranging from precision tests of the Standard Model, to searches for new physics and to the monitoring of nuclear reactors.
We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each ...case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos.
A
bstract
We discuss the phenomenology of right-handed charged currents in the frame-work of the Standard Model Effective Field Theory, in which they arise due to a single gauge-invariant ...dimension-six operator. We study the manifestations of the nine complex couplings of the
W
to right-handed quarks in collider physics, flavor physics, and low-energy precision measurements. We first obtain constraints on the couplings under the assumption that the right-handed operator is the dominant correction to the Standard Model at observable energies. We subsequently study the impact of degeneracies with other Beyond-the-Standard-Model effective interactions and identify observables, both at colliders and low-energy experiments, that would uniquely point to right-handed charged currents.
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