We present the results of the analysis of
η
→
e
+
e
−
γ
and
η
→
e
+
e
−
decays. The experimental data were collected in proton-proton collisions at incident proton kinetic energy 1.4 GeV using the ...WASA detector and the COSY storage ring. We describe the extraction procedure of the
η
meson transition form factor, based on a sample of around 10
8
η
mesons, and show an attempt to search for physics beyond the Standard Model that led to the setting of an upper limit on the coupling between photons and hypothetical dark bosons. We also provide an estimate of the branching ratio upper limit for the very rare
η
→
e
+
e
−
decay.
We report an early result from the ICARUS experiment on the search for a
ν
μ
→
ν
e
signal due to the LSND anomaly. The search was performed with the ICARUS T600 detector located at the Gran Sasso ...Laboratory, receiving CNGS neutrinos from CERN at an average energy of about 20 GeV, after a flight path of ∼730 km. The LSND anomaly would manifest as an excess of
ν
e
events, characterized by a fast energy oscillation averaging approximately to
with probability
. The present analysis is based on 1091 neutrino events, which are about 50 % of the ICARUS data collected in 2010–2011. Two clear
ν
e
events have been found, compared with the expectation of 3.7±0.6 events from conventional sources. Within the range of our observations, this result is compatible with the absence of a LSND anomaly. At 90 % and 99 % confidence levels the limits of 3.4 and 7.3 events corresponding to oscillation probabilities
and
are set respectively. The result strongly limits the window of open options for the LSND anomaly to a narrow region around (Δ
m
2
,sin
2
(2
θ
))
new
=(0.5 eV
2
,0.005), where there is an overall agreement (90 % CL) between the present ICARUS limit, the published limits of KARMEN and the published positive signals of LSND and MiniBooNE Collaborations.
Abstract Purpose/Objective Radiation oncology trainees frequently learn to contour through clinical experience and lectures. A hands-on contouring module was developed to teach delineation of the ...postoperative prostate clinical target volume (CTV) and improve contouring accuracy. Methods Medical students independently contoured a prostate fossa CTV before and after receiving educational materials and live instruction detailing the RTOG approach to contouring this CTV. Metrics for volume overlap and surface distance (Dice similarity coefficient, Hausdorff distance (HD), and mean distance) determined discordance between student and consensus contours. An evaluation assessed perception of session efficacy (1 = “not at all” to 5 = “extremely”; reported as medianinterquartile range). Non-parametric statistical tests were used. Results Twenty-four students at two institutions completed the module, and 21 completed the evaluation (88% response). The content was rated as “quite” important (43.5-5). The module improved comfort contouring a prostate fossa (pre 11-2 vs. post 43-4, p<.01), ability to find references (pre 21-3 vs. post 43.5-4, p<0.01), knowledge of CT prostate/pelvis anatomy (pre 21.5-3 vs. post 33-4, p<.01), and ability to use contouring software tools (pre 22-3.5 vs. post 33-4, p=.01). After intervention, mean DSC increased (0.29 to 0.68, p<0.01) and HD and mean distance both decreased, respectively (42.8 to 30.0, p<.01; 11.5 to 1.9, p<.01). Conclusions A hands-on module to teach CTV delineation to medical students was developed and implemented. Student and expert contours exhibited near “excellent agreement” (as defined in the literature) after intervention. Additional modules to teach target delineation to all educational levels can be developed using this model.
Analysis of the liquid argon purity in the ICARUS T600 TPC Amoruso, S; Aprili, P; Arneodo, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2004, 2004-1-00, Letnik:
516, Številka:
1
Journal Article
Recenzirano
The results reported in this paper are based on the analysis of the data recorded with the first half-module of the ICARUS T600 liquid argon Time Projection Chamber (LAr TPC), during a technical run ...that took place on surface in Pavia (Italy). We include results from the linearity, uniformity and calibration of the electronics, measurements on the electron drift velocity in LAr at different electric fields, as well as the LAr purity achievement of the detector. Two complementary techniques were used to measure the drift electron lifetime inside the active volume: the first, from the data of a purity monitor, gives a measurement localized in space; the second, based on the study of the signals produced by long minimum ionizing tracks crossing the detector, provides a LAr volume averaged value. Both methods yield consistent results over the whole data taking period and are compatible with an uniform LAr purity over the whole volume. The maximal drift electron lifetime value was recorded before the run stop and was about
1.8
ms
. From an interpretation of the observed drift electron lifetime as a function of time, we conclude that the adopted technology would allow for drift distances exceeding
3
m
.
Two-pion production reactions in proton–proton collisions have been studied using the PROMICE/ WASA detector and an internal cluster gas-jet target at the CELSIUS storage ring in Uppsala. The total ...cross sections for the
pp→ppπ
+π
−
,
pp→ppπ
0π
0
and the
pp→pnπ
0π
+
reactions are presented at beam energies ranging from 650 to 775 MeV. An isospin analysis of the amplitudes involved in these three reactions indicates that the excitation of the
N
∗(1440)
followed by direct two pion emission can be the most important amplitude when allowed. However, large contributions from other production mechanisms must also be prevalent to explain the large
pp→pnπ
0π
+
cross section. The data are compared to an extensive model including non-resonant as well as resonant production via
N
∗
and
Δ excitation.
Purpose:
Dose accuracy has been shown to vary with dose per segment and dose rate when delivered with static multileaf collimator (SMLC) intensity modulated radiation therapy (IMRT) by Varian ...C-series MLC controllers. The authors investigated the impact of monitor units (MUs) per segment and dose rate on the dose delivery accuracy of SMLC-IMRT fields on a Varian TrueBeam linear accelerator (LINAC), which delivers dose and manages motion of all components using a single integrated controller.
Methods:
An SMLC sequence was created consisting of ten identical 10 × 10 cm2 segments with identical MUs. Beam holding between segments was achieved by moving one out-of-field MLC leaf pair. Measurements were repeated for various combinations of MU/segment ranging from 1 to 40 and dose rates of 100–600 MU/min for a 6 MV photon beam (6X) and dose rates of 800–2400 MU/min for a 10 MV flattening-filter free photon (10XFFF) beam. All measurements were made with a Farmer (0.6 cm3) ionization chamber placed at the isocenter in a solid–water phantom at 10 cm depth. The measurements were performed on two Varian LINACs: C-series Trilogy and TrueBeam. Each sequence was delivered three times and the dose readings for the corresponding segments were averaged. The effects of MU/segment, dose rate, and LINAC type on the relative dose variation (Δ
i
) were compared using F-tests (α = 0.05).
Results:
On the Trilogy, large Δ
i
was observed in small MU segments: at 1 MU/segment, the maximum Δ
i
was 10.1% and 57.9% at 100 MU/min and 600 MU/min, respectively. Also, the first segment of each sequence consistently overshot (Δ
i
> 0), while the last segment consistently undershot (Δ
i
< 0). On the TrueBeam, at 1 MU/segment, Δ
i
ranged from 3.0% to 4.5% at 100 and 600 MU/min; no obvious overshoot/undershoot trend was observed. F-tests showed statistically significant difference (1 − β) =1.0000 between the Trilogy and the TrueBeam up to 10 MU/segment, at all dose rates greater than 100 MU/min. The linear trend of decreasing dose accuracy as a function of increasing dose rate on the Trilogy is no longer apparent on TrueBeam, even for dose rates as high as 2400 MU/min. Dose inaccuracy averaged over all ten segments in each beam delivery sequence was larger for Trilogy than TrueBeam, with the largest discrepancy (0.2% vs 3%) occurring for 1 MU/segment beams at both 300 and 600 MU/min.
Conclusions:
Earlier generations of Varian LINACs exhibited large dose variations for small MU segments in SMLC-IMRT delivery. Our results confirmed these findings. The dose delivery accuracy for SMLC-IMRT is significantly improved on TrueBeam compared to Trilogy for every combination of low MU/segment (1–10) and high dose rate (200–600 MU/min), in part due to the faster sampling rate (100 vs 20 Hz) and enhanced electronic integration of the MLC controller with the LINAC. SMLC-IMRT can be implemented on TrueBeam with higher dose accuracy per beam (±0.2% vs ±3%) than previous generations of Varian C-series LINACs for 1 MU/segment delivered at 600 MU/min).
This paper reports measurements of two-pion femtoscopic correlations in Be+Be collisions at a beam momentum of 150
A
GeV
/
c
(energy available in the center-of-mass system for nucleon pair
s
NN
=
...16.84
GeV) by the NA61/SHINE experiment at the CERN SPS accelerator. The obtained momentum space correlation functions can be well described by a Lévy distributed source model. The transverse mass dependence of the Lévy source parameters is presented, and their possible theoretical interpretations are discussed. The results show that the Lévy exponent
α
is approximately constant as a function of
m
T
, and far from both the Gaussian case of
α
=
2
or the conjectured value at the critical endpoint,
α
=
0.5
. The radius scale parameter
R
shows a slight decrease in
m
T
, which can be explained as a signature of transverse flow. Finally, an approximately constant trend of the intercept parameter
λ
as a function of
m
T
was observed, similar to previous NA44 S + Pb results (obtained with a Gaussian approximation, but unlike RHIC results).
Measurements of multiplicity and transverse momentum fluctuations of charged particles were performed in inelastic p+p interactions at 20, 31, 40, 80, and 158
GeV
/
c
beam momentum. Results for the ...scaled variance of the multiplicity distribution and for three strongly intensive measures of multiplicity and transverse momentum fluctuations
Δ
P
T
,
N
,
Σ
P
T
,
N
and
Φ
p
T
are presented. For the first time the results on fluctuations are fully corrected for experimental biases. The results on multiplicity and transverse momentum fluctuations significantly deviate from expectations for the independent particle production. They also depend on charges of selected hadrons. The string-resonance Monte Carlo models
Epos
and
U
r
qmd
do not describe the data. The scaled variance of multiplicity fluctuations is significantly higher in inelastic p+p interactions than in central Pb+Pb collisions measured by NA49 at the same energy per nucleon. This is in qualitative disagreement with the predictions of the Wounded Nucleon Model. Within the statistical framework the enhanced multiplicity fluctuations in inelastic p+p interactions can be interpreted as due to event-by-event fluctuations of the fireball energy and/or volume.
The pp → ppη reaction has been measured at six energies close to threshold, from 1258 MeV to 1352 MeV, using an internal cluster gas jet target in the CELSIUS storage ring. The η is detected through ...its decay photons, in an array of CsI detectors, and the forward-going protons are detected in a plastic scintillator spectrometer. A complete event reconstruction is obtained at the higher energies in the measured interval. The new data, together with earlier data, give an accurate determination of the energy dependence close to threshold. The influence of the η-proton FSI is seen in the total cross section data as well as in a Dalitz plot of the η-p invariant mass distributions.
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