A
bstract
Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on proton-proton collision data ...corresponding to an integrated luminosity of 3.2 fb
−1
at
s
=
13
TeV recorded in 2015. Two searches are performed, one targeted at a spin-2 particle of mass larger than 500 GeV, using Randall-Sundrum graviton states as a benchmark model, and one optimized for a spin-0 particle of mass larger than 200 GeV. Varying both the mass and the decay width, the most significant deviation from the background-only hypothesis is observed at a diphoton invariant mass around 750 GeV with local significances of 3.8 and 3.9 standard deviations in the searches optimized for a spin-2 and spin-0 particle, respectively. The global significances are estimated to be 2.1 standard deviations for both analyses. The consistency between the data collected at 13 TeV and 8 TeV is also evaluated. Limits on the production cross section times branching ratio to two photons for the two resonance types are reported.
Chromium(VI) transport across supported liquid membranes (SLMs) and polymer inclusion membranes (PIMs) with tertiary amines and quaternary ammonium salt (Aliquat 336) from chloride acidic aqueous ...solution to 0.1
M NaOH has been studied. The initial flux of Cr(VI) decreases linearly with logarithm of
n-octanol/water partition coefficient increase for R
3N amines (R
=
n-C
6H
13–
n-C
12H
25). The chromate ions are transported across polymer inclusion membranes with lower rate using polyvinyl chloride (PVC) instead of cellulose triacetate (CTA) support. The decreasing of Cr(VI) initial fluxes in following order of plasticizers:
o-nitrophenyl pentyl ether
>
bis(2-ethylhexyl) adipate
>
dibutyl phtalate was observed. The comparative Cr(VI) transport studies of bulk, supported and polymer inclusion membranes were done. The highest permeability coefficient values for Cr(VI) was found for SLM, while the lowers values were observed for BLM. The repeated transport experiments of SLM and PIM were shown and the stability of PIM was described using the Danesi's thermodynamic model. The long-term integrity of PIM was found. Non-contact atomic force microscope was applied to obtain images of pores in polymer inclusion membranes.
The results of a search for gluino and squark pair production with the pairs decaying via the lightest charginos into a final state consisting of two W bosons, the lightest neutralinos ((chi) over ...tilde (0)(1)), and quarks, are presented: the signal is characterised by the presence of a single charged lepton (e(+/-) or mu(+/-)) from a W boson decay, jets, and missing transverse momentum. The analysis is performed using 139 fb(-1) of proton-proton collision data taken at a centre-of-mass energy root s = 13 delivered by the Large Hadron Collider and recorded by the ATLAS experiment. No statistically significant excess of events above the Standard Model expectation is found. Limits are set on the direct production of squarks and gluinos in simplified models. Masses of gluino (squark) up to 2.2 (1.4 ) are excluded at 95% confidence level for a light (chi) over tilde (0)(1).
Measurements of longitudinal flow correlations are presented for charged particles in the pseudorapidity range
|
η
|
<
2.4
using 7 and 470
μ
b
-
1
of Pb+Pb collisions at
s
NN
=
2.76
and 5.02 TeV, ...respectively, recorded by the ATLAS detector at the LHC. It is found that the correlation between the harmonic flow coefficients
v
n
measured in two separated
η
intervals does not factorise into the product of single-particle coefficients, and this breaking of factorisation, or flow decorrelation, increases linearly with the
η
separation between the intervals. The flow decorrelation is stronger at 2.76 TeV than at 5.02 TeV. Higher-order moments of the correlations are also measured, and the corresponding linear coefficients for the
k
th
-moment of the
v
n
are found to be proportional to
k
for
v
3
, but not for
v
2
. The decorrelation effect is separated into contributions from the magnitude of
v
n
and the event-plane orientation, each as a function of
η
. These two contributions are found to be comparable. The longitudinal flow correlations are also measured between
v
n
of different order in
n
. The decorrelations of
v
2
and
v
3
are found to be independent of each other, while the decorrelations of
v
4
and
v
5
are found to be driven by the nonlinear contribution from
v
2
2
and
v
2
v
3
, respectively.
The BaBar detector: Upgrades, operation and performance Couderc, F.; Prudent, X.; Groysman, Y. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2013, Letnik:
729, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The BaBar detector operated successfully at the PEP-II asymmetric e+e− collider at the SLAC National Accelerator Laboratory from 1999 to 2008. This report covers upgrades, operation, and performance ...of the collider and the detector systems, as well as the trigger, online and offline computing, and aspects of event reconstruction since the beginning of data taking.
A
bstract
A search for pair production of vector-like quarks, both up-type (
T
) and down-type (
B
), as well as for four-top-quark production, is presented. The search is based on
pp
collisions at
s
...=
8
TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 20.3 fb
−1
. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon with high transverse momentum, large missing transverse momentum and multiple jets. Dedicated analyses are performed targeting three cases: a
T
quark with significant branching ratio to a
W
boson and a
b
-quark
T
T
¯
→
Wb
+
X
, and both a
T
quark and a
B
quark with significant branching ratio to a Higgs boson and a third-generation quark (
T
T
¯
→
H
t
+
X
and
B
B
¯
→
H
b
+
X
respectively). No significant excess of events above the Standard Model expectation is observed, and 95% CL lower limits are derived on the masses of the vector-like
T
and
B
quarks under several branching ratio hypotheses assuming contributions from
T
→
Wb
,
Zt
,
Ht
and
B
→
Wt
,
Zb
,
Hb
decays. The 95% CL observed lower limits on the
T
quark mass range between 715 GeV and 950 GeV for all possible values of the branching ratios into the three decay modes, and are the most stringent constraints to date. Additionally, the most restrictive upper bounds on four-top-quark production are set in a number of new physics scenarios.
This Letter describes a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model in 3.6 fb(-1) of proton-proton collisions with a ...centre-of-mass energy of root s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the smoothly falling prediction of the Standard Model. The data are also compared to a Monte Carlo simulation of Standard Model angular distributions derived from the rapidity of the two jets. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% CL, quantum black holes with threshold masses below 8.3 TeV, 8.1 TeV, or 5.1 TeV in three different benchmark scenarios; resonance masses below 5.2 TeV for excited quarks, 2.6 TeV in a W' model, a range of masses starting from mZ' = 1.5 TeVand couplings from g(q) = 0.2 in a Z' model; and contact interactions with a compositeness scale below 12.0 TeV and 17.5 TeV respectively for destructive and constructive interference between the new interaction and QCD processes. These results significantly extend the ATLAS limits obtained from 8 TeV data. Gaussian-shaped contributions to the mass distribution are also excluded if the effective cross-section exceeds values ranging from approximately 50-300 fb for masses below 2 TeV to 2-20 fb for masses above 4 TeV. (C) 2016 CERN for the benefit of the ATLAS Collaboration. This is an open access article under the CC BY license.
A search for the direct production of charginos and neutralinos in final states with at least two hadronically decaying tau leptons is presented. The analysis uses a dataset of pp collisions ...corresponding to an integrated luminosity of 36.1 fb−1 , recorded with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. No significant deviation from the expected Standard Model background is observed. Limits are derived in scenarios of χ˜ + 1 χ˜ − 1 pair production and of χ˜ ± 1 χ˜ 0 2 and χ˜ + 1 χ˜ − 1 production in simplified models where the neutralinos and charginos decay solely via intermediate left-handed staus and tau sneutrinos, and the mass of the τ˜L state is set to be halfway between the masses of the χ˜ ± 1 and the χ˜ 0 1 . Chargino masses up to 630 GeV are excluded at 95% confidence level in the scenario of direct production of χ˜ + 1 χ˜ − 1 for a massless χ˜ 0 1 . Common χ˜ ± 1 and χ˜ 0 2 masses up to 760 GeV are excluded in the case of production of χ˜ ± 1 χ˜ 0 2 and χ˜ + 1 χ˜ − 1 assuming a massless χ˜ 0 1 . Exclusion limits for additional benchmark scenarios with large and small mass-splitting between the χ˜ ± 1 and the χ˜ 0 1 are also studied by varying the τ˜L mass between the masses of the χ˜ ± 1 and the χ˜ 0 1 .
A review with more than 60 references covering macrocycle and macromolecular compounds, i.e. crown ethers, ionizable lariat ethers, calixarenes, calix crowns, as well as macrocycle polymers (for ...example, cyclodextrins), and macromolecular compounds, i.e. acyclic polyethers used as ion carriers in transport across liquid membranes for metal ions selective removal will be presented. The recent literature data as well as our own research results (published in the last 8 years) on metal ions removal and separation will be summarized. Recent developments of the lariat ethers application as ion carriers for alkali metal and alkaline earth metal cations, as well as heavy metal ions removal and separation will be presented in this review. The effect of structural studies of crown ring size variation, lipophilic and acidic group attachments for lariat ethers with carboxylic and other acidic groups on the selectivity and efficiency of metal cations transport will also be presented. Also, the effect of a counter anion presence will be performed. The examples of metal ions selective removal using various other ion carriers such as calixarenes, calixcrown ethers, cyclodextrins and their polymers as well as acyclic polyethers will also be shown.
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