A
bstract
We describe a proposal to add a set of very forward detectors to the CMS experiment for the high-luminosity era of the Large Hadron Collider to search for beyond the standard model ...long-lived particles, such as dark photons, heavy neutral leptons, axion-like particles, and dark Higgs bosons. The proposed subsystem is called
FACET
for
F
orward-
A
perture
C
MS
E
x
T
ension, and will be sensitive to any particles that can penetrate at least 50 m of magnetized iron and decay in an 18 m long, 1 m diameter vacuum pipe. The decay products will be measured in detectors using identical technology to the planned CMS Phase-2 upgrade.
Particle physics today faces the challenge of explaining the mystery of dark matter, the origin of matter over anti-matter in the Universe, the origin of the neutrino masses, the apparent fine-tuning ...of the electro-weak scale, and many other aspects of fundamental physics. Perhaps the most striking frontier to emerge in the search for answers involves new physics at mass scales comparable to familiar matter, below the GeV-scale, or even radically below, down to sub-eV scales, and with very feeble interaction strength. New theoretical ideas to address dark matter and other fundamental questions predict such feebly interacting particles (FIPs) at these scales, and indeed, existing data provide numerous hints for such possibility. A vibrant experimental program to discover such physics is under way, guided by a systematic theoretical approach firmly grounded on the underlying principles of the Standard Model. This document represents the report of the FIPs 2022 workshop, held at CERN between the 17 and 21 October 2022 and aims to give an overview of these efforts, their motivations, and the decadal goals that animate the community involved in the search for FIPs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
3.
Feebly-interacting particles Carenza, Pierluca; Milstead, David A.; Wallisch, Benjamin
The European physical journal. C, Particles and fields,
12/2023, Letnik:
83, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Particle physics today faces the challenge of explaining the mystery of dark matter, the origin of matter over anti-matter in the Universe, the origin of the neutrino masses, the apparent fine-tuning ...of the electro-weak scale, and many other aspects of fundamental physics. Perhaps the most striking frontier to emerge in the search for answers involves new physics at mass scales comparable to familiar matter, below the GeV-scale, or even radically below, down to sub-eV scales, and with very feeble interaction strength. New theoretical ideas to address dark matter and other fundamental questions predict such feebly interacting particles (FIPs) at these scales, and indeed, existing data provide numerous hints for such possibility. A vibrant experimental program to discover such physics is under way, guided by a systematic theoretical approach firmly grounded on the underlying principles of the Standard Model. This document represents the report of the FIPs 2022 workshop, held at CERN between the 17 and 21 October 2022 and aims to give an overview of these efforts, their motivations, and the decadal goals that animate the community involved in the search for FIPs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The first observation of the tt H process in a single Higgs boson decay channel with the full reconstruction of the final state (H → γγ) is presented, with a significance of 6.6 standard deviations ( ...σ ). The C P structure of Higgs boson couplings to fermions is measured, resulting in an exclusion of the pure C P -odd structure of the top Yukawa coupling at 3.2 σ . The measurements are based on a sample of proton-proton collisions at a center-of-mass energy √s = 13 TeV collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb−1. The cross section times branching fraction of the t ¯ t H process is measured to be σtt H Bγγ = 1.56+0.34−0.32 fb , which is compatible with the standard model prediction of 1.13+0.08−0.11 fb . The fractional contribution of the C P -odd component is measured to be fHttCP = 0.00 ± 0.33 .
A search is presented for
slepton pairs produced in proton-proton collisions at a center-of-mass energy of 13
. The search is carried out in events containing two
leptons in the final state, on the ...assumption that each
slepton decays primarily to a
lepton and a neutralino. Events are considered in which each
lepton decays to one or more hadrons and a neutrino, or in which one of the
leptons decays instead to an electron or a muon and two neutrinos. The data, collected with the CMS detector in 2016 and 2017, correspond to an integrated luminosity of 77.2
. The observed data are consistent with the standard model background expectation. The results are used to set 95% confidence level upper limits on the cross section for
slepton pair production in various models for
slepton masses between 90 and 200
and neutralino masses of 1, 10, and 20
. In the case of purely left-handed
slepton production and decay to a
lepton and a neutralino with a mass of 1
, the strongest limit is obtained for a
slepton mass of 125
at a factor of 1.14 larger than the theoretical cross section.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search in an all-jet final state for new massive resonances decaying to
,
, or
boson pairs using a novel analysis method is presented. The analysis is performed on data corresponding to an ...integrated luminosity of 77.3
recorded with the CMS experiment at the LHC at a centre-of-mass energy of 13
. The search is focussed on potential narrow-width resonances with masses above 1.2
, where the decay products of each
or
boson are expected to be collimated into a single, large-radius jet. The signal is extracted using a three-dimensional maximum likelihood fit of the two jet masses and the dijet invariant mass, yielding an improvement in sensitivity of up to 30% relative to previous search methods. No excess is observed above the estimated standard model background. In a heavy vector triplet model, spin-1
and
resonances with masses below 3.5 and 3.8
, respectively, are excluded at 95% confidence level. In a bulk graviton model, upper limits on cross sections are set between 27 and 0.2
for resonance masses between 1.2 and 5.2
, respectively. The limits presented in this paper are the best to date in the dijet final state.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement is presented of differential cross sections for
-channel single top quark and antiquark production in proton-proton collisions at a centre-of-mass energy of 13
by the CMS experiment at ...the LHC. From a data set corresponding to an integrated luminosity of 35.9
, events containing one muon or electron and two or three jets are analysed. The cross section is measured as a function of the top quark transverse momentum (
), rapidity, and polarisation angle, the charged lepton
and rapidity, and the
of the
boson from the top quark decay. In addition, the charge ratio is measured differentially as a function of the top quark, charged lepton, and
boson kinematic observables. The results are found to be in agreement with standard model predictions using various next-to-leading-order event generators and sets of parton distribution functions. Additionally, the spin asymmetry, sensitive to the top quark polarisation, is determined from the differential distribution of the polarisation angle at parton level to be
, in agreement with the standard model prediction.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss
and the four-momentum transfer squared
.... Both processes
and
, i.e. with the proton scattering to either side of the interaction point, are measured, where
includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at
during a dedicated run with
at low instantaneous luminosity and correspond to an integrated luminosity of
. The single-diffractive dijet cross section
, in the kinematic region
,
, with at least two jets with transverse momentum
, and pseudorapidity
, is
. The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of
, is presented as a function of
, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for
values in the range
, is
, where
and
are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A measurement is presented of electroweak (EW) production of a
boson in association with two jets in proton-proton collisions at
. The data sample was recorded by the CMS Collaboration at the LHC and ...corresponds to an integrated luminosity of 35.9
. The measurement is performed for the
jj final state (with
indicating a lepton-neutrino pair, and j representing the quarks produced in the hard interaction) in a kinematic region defined by invariant mass
and transverse momenta
. The cross section of the process is measured in the electron and muon channels yielding
per channel, in agreement with leading-order standard model predictions. The additional hadronic activity of events in a signal-enriched region is studied, and the measurements are compared with predictions. The final state is also used to perform a search for anomalous trilinear gauge couplings. Limits on anomalous trilinear gauge couplings associated with dimension-six operators are given in the framework of an effective field theory. The corresponding 95% confidence level intervals are
,
, and
. These results are combined with the CMS EW
analysis, yielding the constraint on the
coupling:
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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