The LHCb simulation application, Gauss, consists of two independent phases, the generation of the primary event and the tracking of particles produced in the experimental setup. For the LHCb ...experimental program it is particularly important to model B meson decays: the EvtGen code developed in CLEO and BABAR has been chosen and customized for non-coherent B production as occuring in pp collisions at the LHC. The initial proton-proton collision is provided by a different generator engine, currently PYTHIA 6 for massive production of signal and generic pp collisions events. Beam gas events, background events originating from proton halo, cosmics and calibration events for different detectors can be generated in addition to pp collisions. Different generator packages as available in the physics community or specifically developed in LHCb are used for the different purposes. Running conditions affecting the generated events such as the size of the luminous region, the number of collisions occuring in a bunch crossing and the number of spill-over events from neighbouring bunches are modeled via dedicated algorithms appropriately configured. The design of the generator phase of Gauss will be described: a modular structure with well defined interfaces specific to the various tasks, e.g. pp collisions, particle decays, selections, etc. has been chosen. Different implementations are available for the various tasks allowing selecting and combining them as most appropriate at run time as in the case of PYTHIA 6 for pp collisions or HIJING for beam gas. The advantages of such structure, allowing for example to adopt transparently new generators packages, will be discussed.
TORCH pattern recognition and particle identification performance Garcia Martin, L.M.; Blake, T.; Brook, N.H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2023, Letnik:
1055
Journal Article
Recenzirano
Odprti dostop
The TORCH detector aims to provide K/π (K/p) separation up to a momentum of about 10 (15) ▪ by measuring their time-of-flight at the LHCb detector. Prompt Cherenkov photons are produced in a quartz ...radiator bar of 10 mm thickness, and propagated via total internal reflection to the periphery of the detector, where they are focused onto an array of microchannel plate photomultipliers that measure the photon arrival time and position. Pattern recognition techniques are used to compare the likelihood that the detector image is due to a given particle hypothesis. Good performance is obtained even for very high detector occupancies.
The TORCH time-of-flight detector Harnew, N.; Gao, R.; Hadavizadeh, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2023, Letnik:
1048
Journal Article
Recenzirano
Odprti dostop
TORCH is a large-area time-of-flight (ToF) detector, proposed for the Upgrade-II of the LHCb experiment. It will provide charged hadron identification over a 2–20 GeV/c momentum range, given a 9.5m ...flight distance from the LHC interaction point. To achieve this level of performance, a 15ps timing resolution per track is required. A TORCH prototype module having a 1250×660×10mm3 fused-silica radiator plate and equipped with two MCP-PMTs has been tested in a 8GeV/c CERN test-beam. Single-photon time resolutions of between 70–100ps have been achieved, dependent on the beam position in the radiator. The measured photon yields agree with expectations.
The LHCb simulation application. Gauss, consists or two independent phases, the generation of the primary event and the tracking of particles produced in the experimental setup. For the LHCh ...experimental program it is particularly important to model B meson decays: the EvtGcn code developed in CLEO and BaBah has been chosen and customized for non-coherent B production as occurring in pp collisions at the LHC, The initial proton-proton collision is provided by a different generator engine, currently PYTHIA 6 for massive production of signal and generic pp collisions events. Beam gas events, background events originating from proton halo, cosmics and calibration events for different detectors can be generated in addition to pp collisions. Different generator packages as available in the physics community or specifically developed in LHCb are used for the different purposes. Running conditions affecting the events generated such as the size of the luminous region, the number of collisions occuring in a bunch crossing and the number of spill-over events from neighbouring bunches are modeled via dedicated algorithms appropriately configured. The design of the generator phase of Gauss will be described: a modular structure with well defined interfaces specific to the various tasks, e.g. pp collisions, particles' decays, selections, etc. has been chosen. Different implementations are available for the various tasks allowing selecting and combining them as most appropriate at run time as in the case of Pythia 6 im pp collisions or HIJING for beam gas. The advantages of such structure, allowing for example to adopt transparently new generators packages will be discussed.
A
bstract
The exclusive photoproduction reactions
γp
→
J/ψ
(1
S
)
p
and
γp
→
ψ
(2
S
)
p
have been measured at an
ep
centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated ...luminosity of 373 pb
−
1
. The measurement was made in the kinematic range 30
< W <
180 GeV,
Q
2
<
1 GeV
2
and |
t
|
<
1 GeV
2
, where
W
is the photon-proton centre-of-mass energy,
Q
2
is the photon virtuality and
t
is the squared four-momentum transfer at the proton vertex. The decay channels used were
J/ψ
(1
S
)
→ μ
+
μ
−
,
ψ
(2
S
)
→ μ
+
μ
−
and
ψ
(2
S
)
→ J/ψ
(1
S
)
π
+
π
−
with subsequent decay
J/ψ
(1
S
)
→ μ
+
μ
−
. The ratio of the production cross sections,
R
=
σ
ψ
(2
S
)
/σ
J/ψ
(1
S
)
, has been measured as a function of
W
and |
t
| and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.
Hypoplastic left heart syndrome (HLHS) is frequently diagnosed prenatally, but this has not been shown to improve surgical outcome.
We reviewed patients with HLHS between July 1992 and March 1999 to ...determine the influence of prenatal diagnosis on preoperative clinical status, outcomes of stage 1 surgery, and parental decisions regarding care. Of 88 patients, 33 were diagnosed prenatally and 55 after birth. Of 33 prenatally diagnosed patients, 22 were live-born, and pregnancy was terminated in 11. Of 22 prenatally diagnosed patients who were live-born, 14 underwent surgery, and parents elected to forego treatment in 8. Of 55 patients diagnosed postnatally, 38 underwent surgery, and 17 did not because of parental decisions or clinical considerations. Prenatally diagnosed patients were less likely to undergo surgery than patients diagnosed after birth (P:=0.008). Among live-born infants, there was a similar rate of nonintervention. Among patients who underwent surgery, survival was 75% (39/52). All patients who had a prenatal diagnosis and underwent surgery survived, whereas only 25 of 38 postnatally diagnosed patients survived (P:=0.009). Patients diagnosed prenatally had a lower incidence of preoperative acidosis (P:=0.02), tricuspid regurgitation (P:=0.001), and ventricular dysfunction (P:=0.004). They were also less likely to need preoperative inotropic medications or bicarbonate (P:=0.005). Preoperative factors correlating with early mortality included postnatal diagnosis (P:=0.009), more severe acidosis (P:=0.03), need for bicarbonate or inotropes (P:=0.008 and 0.04), and ventricular dysfunction (P:=0.05).
Prenatal diagnosis of HLHS was associated with improved preoperative clinical status and with improved survival after first-stage palliation in comparison with patients diagnosed after birth.
A new measurement of inclusive-jet cross sections in the Breit frame in neutral current deep inelastic scattering using the ZEUS detector at the HERA collider is presented. The data were taken in the ...years 2004–2007 at a centre-of-mass energy of
318
GeV
and correspond to an integrated luminosity of
347
pb
-
1
. The jets were reconstructed using the
k
t
-algorithm in the Breit reference frame. They have been measured as a function of the squared momentum transfer,
Q
2
, and the transverse momentum of the jets in the Breit frame,
p
⊥
,
Breit
. The measured jet cross sections are compared to previous measurements and to perturbative QCD predictions. The measurement has been used in a next-to-next-to-leading-order QCD analysis to perform a simultaneous determination of parton distribution functions of the proton and the strong coupling, resulting in a value of
α
s
(
M
Z
2
)
=
0.1142
±
0.0017
(experimental/fit)
-
0.0007
+
0.0006
(model/parameterisation)
-
0.0004
+
0.0006
(scale)
, whose accuracy is improved compared to similar measurements. In addition, the running of the strong coupling is demonstrated using data obtained at different scales.
Abstract The exclusive photoproduction reactions γp → J/ψ(1S)p and γp → ψ(2S)p have been measured at an ep centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated ...luminosity of 373 pb −1. The measurement was made in the kinematic range 30 < W < 180 GeV, Q 2 < 1 GeV2 and |t| < 1 GeV2, where W is the photon-proton centre-of-mass energy, Q 2 is the photon virtuality and t is the squared four-momentum transfer at the proton vertex. The decay channels used were J/ψ(1S) → μ + μ − , ψ(2S) → μ + μ − and ψ(2S) → J/ψ(1S)π + π − with subsequent decay J/ψ(1S) → μ + μ − . The ratio of the production cross sections, R = σ ψ(2S) /σ J/ψ(1S), has been measured as a function of W and |t| and compared to previous data in photoproduction and deep inelastic scattering and with predictions of QCD-inspired models of exclusive vector-meson production, which are in reasonable agreement with the data.
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