A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb
-
1
of proton–proton collision ...data at
s
=
13
TeV
recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-rich cascade decays, substantially improving on previous limits. In the GMSB model considered, supersymmetry-breaking scale (
Λ
) values below
92
TeV
are excluded at the 95% confidence level, corresponding to gluino masses below
2000
GeV
. For large values of
tan
β
, values of
Λ
up to
107
TeV
and gluino masses up to
2300
GeV
are excluded. In the simplified model, gluino masses are excluded up to
1570
GeV
for neutralino masses around
100
GeV
. Neutralino masses below
700
GeV
are excluded for all gluino masses between 800 and
1500
GeV
, while the strongest exclusion of
750
GeV
is achieved for gluino masses around
1450
GeV
.
A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb
-
1
of proton–proton ...collision data at
s
=
8
TeV
. The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at
95
%
confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the
87
GeV
LEP limit to the top squark mass, lower limits between 490 and
650
GeV
are placed on the top squark mass within the model considered.
The internal thoracic artery (ITA) is the conduit of choice in coronary bypass grafting, due to the excellent long-term results achieved using it. However, increased incidence of sternal infections ...after pedicled ITA harvesting has revived interest in the morphology of sternal blood supply. Our aim was to discuss the topography of the sternal branches with emphasis on internal thoracic artery harvesting.
This study was conducted on 50 fresh specimens of the anterior thorax wall. Radio-opaque material was injected and angiograms of the ITA were performed. Subsequently, the specimens were preserved and a dry dissection of each ITA and its branches was carried out.
In dry dissected specimens, four types of vessels were identified that have the potential to carry blood to the sternum after harvesting the ITA. In the first group, the artery to the sternum also supplies the intercostal space. In the second morphologic variant, the sternal branch gives off the perforating and anterior intercostal arteries. In the third group, we classified the common branch of the sternal and perforating arteries. In the fourth group, the sternal artery originated from the ITA as an independent branch.
For sternal-intercostal, perforating-intercostal, and sternal-perforating branches to function as collaterals after ITA harvesting, the common trunk of origin must remain intact. Based on morphologic data, we recommend ligating the common trunk as close as possible to the ITA; in this way, collateral blood flow to the sternum remains intact.
This Letter presents a measurement of W±Z production in 1.02 fb−1 of pp collision data at s=7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, ...muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1±1.4(stat.)−2.0+4.1(syst.) events. The total cross section for W±Z production for Z/γ⁎ masses within the range 66 GeV to 116 GeV is determined to be σWZtot=20.5−2.8+3.1(stat.)−1.3+1.4(syst.)−0.8+0.9(lumi.) pb, which is consistent with the Standard Model expectation of 17.30.8+1.3 pb. Limits on anomalous triple gauge boson couplings are extracted.
The accurate simulation of additional interactions at the ATLAS experiment for the analysis of proton–proton collisions delivered by the Large Hadron Collider presents a significant challenge to the ...computing resources. During the LHC Run 2 (2015–2018), there were up to 70 inelastic interactions per bunch crossing, which need to be accounted for in Monte Carlo (MC) production. In this document, a new method to account for these additional interactions in the simulation chain is described. Instead of sampling the inelastic interactions and adding their energy deposits to a hard-scatter interaction one-by-one, the inelastic interactions are presampled, independent of the hard scatter, and stored as combined events. Consequently, for each hard-scatter interaction, only one such presampled event needs to be added as part of the simulation chain. For the Run 2 simulation chain, with an average of 35 interactions per bunch crossing, this new method provides a substantial reduction in MC production CPU needs of around 20%, while reproducing the properties of the reconstructed quantities relevant for physics analyses with good accuracy.
Objective: Life expectancy of cryopreserved allografts implanted in infants is different from those implanted in adults. A morphological study of explanted allograft heart valves was performed to ...determine the mechanism of deterioration and to compare cryopreserved arterial and heart valve allografts from adult patients with those explanted from infants. Method: Between 1987 and 1996, 209 cryopreserved allografts were implanted: 125 valved conduits or monocusps to reconstruct the right ventricular outflow tract in congenital heart disease, 50 allograft heart valves to treat native aortic and prosthetic aortic valve endocarditis and 34 cryopreserved arterial allografts to replace mycotic aortic aneurysms or infected aortic prosthetic grafts. Two months to 8 years after implantation, 23 heart valve allografts, 11 right-sided and 12 left-sided, and four arterial allografts had to be explanted for reasons such as degeneration, recurrent infection, aneurysm formation or rupture. Besides conventional staining, immunohistochemical detection of cell populations was performed as follows: CD45RO, CD3 and CD43 for T lymphocytes, CD20 for B lymphocytes, CD68 for macrophages, protein S100 for Langerhans-cells, vimentin for fibroblasts, α-actin for smooth muscle cells and factor VIII for endothelial cells. Results: Explanted cryopreserved allografts were all fibrotic, acellular, non-vital and without endothelial cells. The fibrous tissue was preserved. T lymphocytes, indicating rejection, were found in all right-sided allografts from the paediatric population, but only in 9% of left-sided valves explanted from adults and in one of the four of arterial allografts. Macrophages and Langerhans-cells were found only in right-sided allografts from paediatric patients. Conclusion: Right-sided cryopreserved allografts from a paediatric population showed ongoing cellular rejection. By contrast, there was only a weak T-cell mediated rejection to adult heart valve and arterial allografts. Therefore, similar long-term results can be expected in adult arterial and heart valve allografts, whereas longevity of right-sided heart valve allograft in the paediatric age group seems endangered by cellular rejection.
A
bstract
The production of single top quarks and top antiquarks via the
t
-channel exchange of a virtual
W
boson is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV at the ...LHC using 140 fb
−
1
of ATLAS data. The total cross-sections are determined to be
σ
tq
=
137
−
8
+
8
pb and
σ
t
¯
q
=
84
−
5
+
6
pb for top-quark and top-antiquark production, respectively. The combined cross-section is found to be
σ
tq
+
t
¯
q
=
221
−
13
+
13
pb and the cross-section ratio is
R
t
=
σ
tq
/
σ
t
¯
q
=
1.636
−
0.034
+
0.036
. The predictions at next-to-next-to-leading-order in quantum chromodynamics are in good agreement with these measurements. The predicted value of
R
t
using different sets of parton distribution functions is compared with the measured value, demonstrating the potential to further constrain the functions when using this result in global fits. The measured cross-sections are interpreted in an effective field theory approach, setting limits at the 95% confidence level on the strength of a four-quark operator and an operator coupling the third quark generation to the Higgs boson doublet:
−
0.37
<
C
Qq
3
,
1
/
Λ
2
<
0.06
and
−
0.87
<
C
ϕQ
3
/
Λ
2
<
1.42
. The constraint
|V
tb
|
> 0.95 at the 95% confidence level is derived from the measured value of
σ
tq
+
t
¯
q
, assuming that the
Wtb
interaction is a left-handed weak coupling and that |
V
tb
| ≫ |
V
td
|, |
V
ts
|. In a more general approach, pairs of CKM matrix elements involving top quarks are simultaneously constrained, leading to confidence contours in the corresponding two-dimensional parameter spaces.
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