Purpose
For determining small‐field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) ...detector with output image acquisition and processing to allow real‐time monitoring of profile and output factor.
Materials and methods
The employed detector is a SciFi detector made of tissue‐equivalent scintillating plastic fibers arranged in 6‐layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal–oxide–semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water‐equivalent phantom and irradiated by a 6 MV photon beam.
Results
The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real‐time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro‐cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes.
Conclusions
We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS‐483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI‐LINAC.
The Beam Gas Vertex detector (BGV) is an innovative beam profile monitor based on the reconstruction of beam-gas interaction vertices which is being developed as part of the High Luminosity LHC ...project. Tracks are identified using several planes of scintillating fibres, located outside the beam vacuum chamber and perpendicular to the beam axis. The gas pressure in the interaction volume is adjusted such as to provide an adequate trigger rate, without disturbing the beam. A BGV demonstrator monitoring one of the two LHC beams was fully installed and commissioned in 2016. First data and beam size measurements show that the complete detector and data acquisition system is operating as expected. The BGV operating parameters are now being optimised and the reconstruction algorithms developed to produce accurate and fast reconstruction on a CPU farm in order to provide real time beam profile measurements to the LHC operators.
The Beam Gas Vertex detector (BGV) is an innovative beam profile monitor based on the reconstruction of beam-gas interaction vertices which is being developed as part of the High Luminosity LHC ...project. Tracks are identified using several planes of scintillating fibres, located outside the beam vacuum chamber and perpendicular to the beam axis. The gas pressure in the interaction volume is adjusted such as to provide an adequate trigger rate, without disturbing the beam. A BGV demonstrator monitoring one of the two LHC beams was fully installed and commissioned in 2016. First data and beam size measurements show that the complete detector and data acquisition system is operating as expected. The BGV operating parameters are now being optimised and the reconstruction algorithms developed to produce accurate and fast reconstruction on a CPU farm in order to provide real time beam profile measurements to the LHC operators.
The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample ...corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)\mu ^(-/+), with the Ds^(+/-) particle decaying in the \phi\pi^(+/-) mode. The Ds^(+/-)\mu ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.
Abstract The cross-sections of $$\psi {(2S)}$$ ψ(2S) meson production in proton-proton collisions at $$\sqrt{s} =13\text { TeV} $$ s=13TeV are measured with a data sample collected by the LHCb ...detector corresponding to an integrated luminosity of $$275\text { pb} ^{-1} $$ 275pb-1 . The production cross-sections for prompt $$\psi {(2S)}$$ ψ(2S) mesons and those for $$\psi {(2S)}$$ ψ(2S) mesons from b-hadron decays ($${\psi {(2S)}} \text{-from- }{b} $$ ψ(2S)-from-b ) are determined as functions of the transverse momentum, $$p_{\mathrm {T}}$$ pT , and the rapidity, y, of the $$\psi {(2S)}$$ ψ(2S) meson in the kinematic range $$2<p_{\mathrm {T}} <20\text { GeV/}c $$ 2<pT<20GeV/c and $$2.0<y<4.5$$ 2.0<y<4.5 . The production cross-sections integrated over this kinematic region are $$\begin{aligned} \begin{aligned}&\sigma (\text{ prompt } {\psi {(2S)}},13\text { TeV})\\&\quad =1.430\pm 0.005\text { (stat)} \pm 0.099\text { (syst)} \,\upmu \text {b} ,\\&\sigma ({\psi {(2S)}} \text{-from- }{b},13\text { TeV})\\&\quad =0.426\pm 0.002\text { (stat)} \pm 0.030\text { (syst)} \,\upmu \text {b} . \end{aligned} \end{aligned}$$ σ(promptψ(2S),13TeV)=1.430±0.005(stat)±0.099(syst)μb,σ(ψ(2S)-from-b,13TeV)=0.426±0.002(stat)±0.030(syst)μb. A new measurement of $$\psi {(2S)}$$ ψ(2S) production cross-sections in pp collisions at $$\sqrt{s}=7\text { TeV} $$ s=7TeV is also performed using data collected in 2011, corresponding to an integrated luminosity of $$614\text { pb} ^{-1} $$ 614pb-1 . The integrated production cross-sections in the kinematic range $$3.5<p_{\mathrm {T}} <14\text { GeV/}c $$ 3.5<pT<14GeV/c and $$2.0<y<4.5$$ 2.0<y<4.5 are $$\begin{aligned} \begin{aligned}&\sigma (\text{ prompt } {\psi {(2S)}},7\text { TeV})\\&\quad =0.471\pm 0.001\text { (stat)} \pm 0.025\text { (syst)} \,\upmu \text {b} ,\\&\sigma ({\psi {(2S)}} \text{-from- }{b},7\text { TeV})\\&\quad =0.126\pm 0.001\text { (stat)} \pm 0.008\text { (syst)} \,\upmu \text {b} . \end{aligned} \end{aligned}$$ σ(promptψ(2S),7TeV)=0.471±0.001(stat)±0.025(syst)μb,σ(ψ(2S)-from-b,7TeV)=0.126±0.001(stat)±0.008(syst)μb. All results show reasonable agreement with theoretical calculations.
First observation of the decay Bs -> D0bar phi is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb^-1, collected by the LHCb experiment at a centre-of-mass energy ...of 7 TeV. The significance of the signal is 6.2 standard deviations. The branching fraction is measured relative to that of the decay Bs -> D0bar K*0bar to be 0.069 +/- 0.013 (stat) +/- 0.007 (syst). The first measurement of the ratio of branching fractions for the decays Bs -> D0bar K*0bar and Bd->D0bar K*0 is found to be 7.8 +/- 0.7 (stat) +/- 0.3 (syst) +/- 0.6 (f_s/f_d), where the last uncertainty is due to the ratio of the Bs and Bd fragmentation fractions.
A
bstract
The production cross-sections of
B
mesons are measured in
pp
collisions at a centre-of-mass energy of 7 TeV, using data collected with the LHCb detector corresponding to a integrated ...luminosity of 0.36 fb
−1
. The
B
+
,
B
0
and
$ B_s^0 $
mesons are reconstructed in the exclusive decays
B
+
→
J
/
ψK
+
,
B
0
→
J
/
ψK
*0
and
$ B_s^0\to {J \left/ {{\psi \phi }} \right.} $
, with
J
/
ψ
→
μ
+
μ
−
,
K
*0
→
K
+
π
−
and
ϕ
→
K
+
K
−
. The differential cross-sections are measured as functions of
B
meson transverse momentum
p
T
and rapidity
y
, in the range 0
< p
T
<
40 GeV
/c
and 2
.
0
< y <
4
.
5. The integrated cross-sections in the same
p
T
and
y
ranges, including charge-conjugate states, are measured to be
$ \begin{array}{*{20}{c}} {\sigma \left( {pp\to {B^{+}}+X} \right)=38.9\pm 0.3\left( {\mathrm{stat}.} \right)\pm 2.5\left( {\mathrm{syst}.} \right)\pm 1.3\left( {\mathrm{norm}.} \right)\upmu \mathrm{b},} \hfill \\ {\sigma \left( {pp\to {B^0}+X} \right)=38.1\pm 0.6\left( {\mathrm{stat}.} \right)\pm 3.7\left( {\mathrm{syst}.} \right)\pm 4.7\left( {\mathrm{norm}.} \right)\upmu \mathrm{b},} \hfill \\ {\sigma \left( {pp\to B_s^0+X} \right)=10.5\pm 0.2\left( {\mathrm{stat}.} \right)\pm 0.8\left( {\mathrm{syst}.} \right)\pm 1.0\left( {\mathrm{norm}.} \right)\upmu \mathrm{b},} \hfill \\ \end{array} $
where the third uncertainty arises from the pre-existing branching fraction measurements.
An analysis of $B^+ \to K_{\rm \scriptscriptstyle S}^0 \pi^+$ and $B^+ \to K_{\rm \scriptscriptstyle S}^0 K^+$ decays is performed with the LHCb experiment. The $pp$ collision data used correspond to ...integrated luminosities of $1{\,fb}^{-1}$ and $2{\,fb}^{-1}$ collected at centre-of-mass energies of $\sqrt{s}=7\mathrm{\,Te\kern -0.1em V}$ and $\sqrt{s}=8\mathrm{\,Te\kern -0.1em V}$, respectively. The ratio of branching fractions and the direct {\it CP} asymmetries are measured to be $\mathcal{B}(B^+ \to K_{\rm \scriptscriptstyle S}^0 K^+)/\mathcal{B}(B^+ \to K_{\rm \scriptscriptstyle S}^0 \pi^+) = 0.064 \pm 0.009\textrm{(stat.)} \pm 0.004\textrm{(syst.)}$, $\mathcal{A}^{\it CP}(B^+ \to K_{\rm \scriptscriptstyle S}^0 \pi^+) = -0.022 \pm 0.025\textrm{(stat.)} \pm 0.010\textrm{(syst.)}$ and $\mathcal{A}^{\it CP}(B^+ \to K_{\rm \scriptscriptstyle S}^0 K^+) = -0.21 \pm 0.14\textrm{(stat.)} \pm 0.01\textrm{(syst.)}$. The data sample taken at $\sqrt{s}=7\mathrm{\,Te\kern -0.1em V}$ is used to search for $B_c^+ \to K_{\rm \scriptscriptstyle S}^0 K^+$ decays and results in the upper limit $(f_c\cdot\mathcal{B}(B_c^+ \to K_{\rm \scriptscriptstyle S}^0 K^+))/(f_u\cdot\mathcal{B}(B^+ \to K_{\rm \scriptscriptstyle S}^0 \pi^+)) < 5.8\times10^{-2}\textrm{at 90% confidence level}$, where $f_c$ and $f_u$ denote the hadronisation fractions of a $\bar{b}$ quark into a $B_c^+$ or a $B^+$ meson, respectively.
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