A search is reported for pairs of light Higgs bosons (
) produced in supersymmetric cascade decays in final states with small missing transverse momentum. A data set of LHC
collisions collected with ...the CMS detector at
and corresponding to an integrated luminosity of 138
is used. The search targets events where both
bosons decay into pairs that are reconstructed as large-radius jets using substructure techniques. No evidence is found for an excess of events beyond the background expectations of the standard model (SM). Results from the search are interpreted in the next-to-minimal supersymmetric extension of the SM, where a "singlino" of small mass leads to squark and gluino cascade decays that can predominantly end in a highly Lorentz-boosted singlet-like
and a singlino-like neutralino of small transverse momentum. Upper limits are set on the product of the squark or gluino pair production cross section and the square of the branching fraction of the
in a benchmark model containing almost mass-degenerate gluinos and light-flavour squarks. Under the assumption of an SM-like branching fraction,
bosons with masses in the range 40-120
arising from the decays of squarks or gluinos with a mass of 1200-2500
are excluded at 95% confidence level.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Measurements of the associated production of a W boson and a charm (
) quark in proton-proton collisions at a centre-of-mass energy of 8
are reported. The analysis uses a data sample corresponding to ...a total integrated luminosity of 19.7
collected by the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm quark jets are selected using distinctive signatures of charm hadron decays. The product of the cross section and branching fraction
, where
or
, and the cross section ratio
are measured in a fiducial volume and differentially as functions of the pseudorapidity and of the transverse momentum of the lepton from the W boson decay. The results are compared with theoretical predictions. The impact of these measurements on the determination of the strange quark distribution is assessed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for new long-lived particles decaying to leptons using proton-proton collision data produced by the CERN LHC at
is presented. Events are selected with two leptons (an electron and a muon, ...two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10
and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113)
in the
channel (
and
channels). The search is designed to be sensitive to a wide range of models with displaced
,
, and
final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Using a data sample of
proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of
, the
and
decays are observed with significances exceeding ...5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to
and
, where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of
and
mesons,
.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The production of Z boson pairs in proton-proton (
) collisions,
, where
or
, is studied at a center-of-mass energy of 13
with the CMS detector at the CERN LHC. The data sample corresponds to an ...integrated luminosity of 137
, collected during 2016-2018. The
production cross section,
, measured for events with two pairs of opposite-sign, same-flavor leptons produced in the mass region
is consistent with standard model predictions. Differential cross sections are also measured and agree with theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous
and
couplings.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13
, corresponding to an integrated luminosity of 35.9
, ...are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for dark matter particles is performed using events with a Z boson candidate and large missing transverse momentum. The analysis is based on proton-proton collision data at a center-of-mass ...energy of 13
, collected by the CMS experiment at the LHC in 2016-2018, corresponding to an integrated luminosity of 137
. The search uses the decay channels
and
. No significant excess of events is observed over the background expected from the standard model. Limits are set on dark matter particle production in the context of simplified models with vector, axial-vector, scalar, and pseudoscalar mediators, as well as on a two-Higgs-doublet model with an additional pseudoscalar mediator. In addition, limits are provided for spin-dependent and spin-independent scattering cross sections and are compared to those from direct-detection experiments. The results are also interpreted in the context of models of invisible Higgs boson decays, unparticles, and large extra dimensions.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The rate for Higgs (
) bosons production in association with either one (
) or two (
) top quarks is measured in final states containing multiple electrons, muons, or tau leptons decaying to hadrons ...and a neutrino, using proton-proton collisions recorded at a center-of-mass energy of
by the CMS experiment. The analyzed data correspond to an integrated luminosity of 137
. The analysis is aimed at events that contain
,
, or
decays and each of the top quark(s) decays either to lepton+jets or all-jet channels. Sensitivity to signal is maximized by including ten signatures in the analysis, depending on the lepton multiplicity. The separation among
,
, and the backgrounds is enhanced through machine-learning techniques and matrix-element methods. The measured production rates for the
and
signals correspond to
and
of their respective standard model (SM) expectations. The corresponding observed (expected) significance amounts to 4.7 (5.2) standard deviations for
, and to 1.4 (0.3) for
production. Assuming that the Higgs boson coupling to the tau lepton is equal in strength to its expectation in the SM, the coupling
of the Higgs boson to the top quark divided by its SM expectation,
, is constrained to be within
or
, at 95% confidence level. This result is the most sensitive measurement of the
production rate to date.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search is presented for supersymmetric partners of the top quark (top squarks) in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from
quarks, ...and missing transverse momentum. The search uses data from proton-proton collisions at
collected with the CMS detector, corresponding to an integrated luminosity of 137
. Hypothetical signal events are efficiently separated from the dominant top quark pair production background with requirements on the significance of the missing transverse momentum and on transverse mass variables. No significant deviation is observed from the expected background. Exclusion limits are set in the context of simplified supersymmetric models with pair-produced lightest top squarks. For top squarks decaying exclusively to a top quark and a lightest neutralino, lower limits are placed at
confidence level on the masses of the top squark and the neutralino up to 925 and 450
, respectively. If the decay proceeds via an intermediate chargino, the corresponding lower limits on the mass of the lightest top squark are set up to 850
for neutralino masses below 420
. For top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1.4
and 900
respectively for the top squark and the lightest neutralino.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The poor knowledge about the presence of diseases and pests affecting the potato crop in developing countries difficult the understanding of their distribution in agro-ecological systems and ...consequent effect on yield and seed quality. A combination of a monitoring and a field experiment were performed to: (1) determine the incidence and severity of pathogens and pests affecting foliage and seed tubers, (2) determine the influence of altitude and seed sources over seed quality, and (3) determine yield responses to seed quality. Disease and pest monitoring on the foliage and seed tubers was performed in farmers’ fields in the main potato production provinces in Ecuador in 2010. The field experiment was performed in CIP-Quito by planting the evaluated seed tubers from 2010-2011 and registering their individual yield. We found that late blight and flea beetle damages were constantly affecting foliage, whereas black scurf, andean weevil, potato virus S and potato virus X predominantly affected seed tubers. Our data suggest that planting at higher altitudes potentially reduce seed-borne viral diversity, and that pathogens and pests diversity on farmers’ seed tubers is similar regardless the seed source. Yield variation was explained by the following problems in the seed tuber: black scurf, presence of potato virus S, potato yellow vein virus, and presence of mechanical damages. However, these problems varied when seed source or variety changed.
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