In the passive CMOS Strips Project, strip sensors were designed at the University of Bonn and produced by LFoundry in 150 nm technology, with an additional backside processing from IZM Berlin. Up to ...five individual reticules were connected by stitching at the foundry in order to obtain the typical strip lengths required for the LHC Phase-II upgrade of ATLAS or CMS trackers. After dicing, sensors were tested in a probe station and characterised with a Sr90-source as well as laser-based edge- and top-TCT systems. Sensors were also simulated using Sentaurus TCAD. At last, detector modules were constructed from several sensors and thoroughly studied in two beam campaigns at DESY. All of these measurements were performed before and after irradiation. This contribution provides an overview of simulation results, summarises the laboratory measurements and in particular presents first test beam results for irradiated and unirradiated passive CMOS strip sensors. We are demonstrating that large area sensors with sufficient radiation hardness can be obtained by stitching during the CMOS process, and presenting our plans for the next submission in the framework of this project.
A large sample (96) of epitaxial Si PIN photodiodes has been irradiated by
∼1
MeV
neutrons and 24
GeV protons with fluences up to 10
15 equivalent 1
MeV neutrons cm
−2 in order to test their ...suitability for use in the optical readout of the ATLAS semiconductor tracker and pixel detector at the CERN Large Hadron Collider. After an initial reduction of 30% the responsivity remains constant up to the maximum fluence. The rise and fall times are not significantly affected and remain below 1
ns. Although the dark current increases linearly with increasing neutron fluence, its level remains below 100 nA which is negligible in comparison to the operating photocurrent which is above
100
μA
. Enhanced ageing studies at 60°C have also been carried out and no failure has occurred after an equivalent of 360 years of operation.
This Letter presents measurements of the differential cross-sections for inclusive electron and muon production in proton–proton collisions at a centre-of-mass energy of s=7 TeV, using data collected ...by the ATLAS detector at the LHC. The muon cross-section is measured as a function of pT in the range 4<pT<100 GeV and within pseudorapidity |η|<2.5. In addition the electron and muon cross-sections are measured in the range 7<pT<26 GeV and within |η|<2.0, excluding 1.37<|η|<1.52. Integrated luminosities of 1.3 pb−1 and 1.4 pb−1 are used for the electron and muon measurements, respectively. After subtraction of the W/Z/γ⁎ contribution, the differential cross-sections are found to be in good agreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLO calculations with NLL high-pT resummation, and to be sensitive to the effects of NLL resummation.
A search for flavour changing neutral current (FCNC) processes in top-quark decays by the ATLAS Collaboration is presented. Data collected from pp collisions at the LHC at a centre-of-mass energy of ...√s = 7 TeV during 2011, corresponding to an integrated luminosity of 2.1 fb⁻¹, were used. A search was performed for top-quark pair-production events, with one top quark decaying through the t → Zq FCNC (q = u, c) channel, and the other through the Standard Model dominant mode t → Wb. Only the decays of the Z boson to charged leptons and leptonic W-boson decays were considered as signal. Consequently, the final-state topology is characterised by the presence of three isolated charged leptons, at least two jets and missing transverse momentum from the undetected neutrino. No evidence for an FCNC signal was found. An upper limit on the t → Zq branching ratio of BR(t → Zq) < 0.73% is set at the 95% confidence level.
This Letter reports a search for a heavy particle that decays to WW using events produced in pp collisions at s=7TeV. The data were recorded in 2011 by the ATLAS detector and correspond to an ...integrated luminosity of 4.7 fb−1. WW→ℓνℓ′ν′ (ℓ,ℓ′=e or μ) final states are considered and the distribution of the transverse mass of the WW candidates is found to be consistent with Standard Model expectations. Upper limits on the production cross section times branching ratio into W boson pairs are set for Randall–Sundrum and bulk Randall–Sundrum gravitons, which result in observed 95% CL lower limits on the masses of the two particles of 1.23 TeV and 0.84 TeV, respectively.
A search for new charged massive gauge bosons, called W′, is performed with the ATLAS detector at the LHC, in proton–proton collisions at a centre-of-mass energy of s=8 TeV, using a dataset ...corresponding to an integrated luminosity of 20.3 fb−1. This analysis searches for W′ bosons in the W′→tb¯ decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W′ bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W′→tb¯ cross-section times branching ratio and on the W′-boson effective couplings as a function of the W′-boson mass using the CLs procedure. For a left-handed (right-handed) W′ boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.
A
bstract
Measurements of the jet activity in
t
t
¯
events produced in proton-proton collisions at
s
=
8
TeV are presented, using 20.3 fb
−1
of data collected by the ATLAS experiment at the Large ...Hadron Collider. The events were selected in the dilepton
eμ
decay channel with two identified
b
-jets. The numbers of additional jets for various jet transverse momentum (
p
T
) thresholds, and the normalised differential cross-sections as a function of
p
T
for the five highest-
p
T
additional jets, were measured in the jet pseudo-rapidity range |
η
|
<
4
.
5. The gap fraction, the fraction of events which do not contain an additional jet in a central rapidity region, was measured for several rapidity intervals as a function of the minimum
p
T
of a single jet or the scalar sum of
p
T
of all additional jets. These fractions were also measured in different intervals of the invariant mass of the
e
μ
b
b
¯
system. All measurements were corrected for detector effects, and found to be mostly well-described by predictions from next-to-leading-order and leading-order
t
t
¯
event generators with appropriate parameter choices. The results can be used to further optimise the parameters used in such generators.
A measurement is presented of the
ϕ
×
BR
(
ϕ
→
K
+
K
-
)
production cross section at
s
= 7 TeV using
p
p
collision data corresponding to an integrated luminosity of 383
μ
b
-
1
, collected with the ...ATLAS experiment at the LHC. Selection of
ϕ
(1020) mesons is based on the identification of charged kaons by their energy loss in the pixel detector. The differential cross section is measured as a function of the transverse momentum,
p
T
,
ϕ
, and rapidity,
y
ϕ
, of the
ϕ
(1020) meson in the fiducial region 500
<
p
T
,
ϕ
<
1200 MeV,
|
y
ϕ
|
<
0.8, kaon
p
T
,
K
>
230 MeV and kaon momentum
p
K
<
800 MeV. The integrated
ϕ
(
1020
)
-meson production cross section in this fiducial range is measured to be
σ
ϕ
×
BR
(
ϕ
→
K
+
K
-
)
= 570
±
8 (stat)
±
66 (syst)
±
20 (lumi)
μ
b
.
We present trace element data for HFSE-rich minerals (titanite, eudialyte, Ti-bearing andradite, zircon) from plutonic rocks of the Eocene Tamazeght complex, High Atlas Mountains, Morocco. In most ...lithologies significant amounts of titanite are present and as such, titanite fractionation played a major role in the evolution of the HFSE budget of the whole complex. By combining our data with published titanite–melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters (Zr/Hf, Nb/Ta, La/Lu and Th/U ratios) during differentiation of silicate melts in detail. Based upon this, we further discuss the genetic relationships between the various rock types present in the Tamazeght complex and show that the above-mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite.
Zircon, eudialyte and Ti-bearing andradite are generally rare or are restricted to localized rock units. Despite their scarcity, each of them can have a significant effect upon the HFSE budget in their evolving magmas. Here, we derive first estimations of eudialyte–melt partition coefficients for REE. Application of these data to eudialyte-bearing rocks of the Ilímaussaq complex (South Greenland), and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations.
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