Single photon detection with the multi-anode CLAS12 RICH detector Contalbrigo, M.; Aaron, E.; Balossino, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
952
Journal Article
Recenzirano
Odprti dostop
The first module of the hybrid-optics large-area CLAS12 RICH at JLab has been recently put into operation using for the first time the well known Hamamatsu H8500 MAPMT and the new single-photon ...dedicated H12700, for a total of about 400 MAPMTs and 25000 pixels. The photon detector must efficiently detect single photons in the visible and near-UV light region, provide a fast response for background rejection and pattern recognition, and have a spatial resolution of less than 1 cm over an area of ≈ 1 m2.
Each front-end readout unit is composed of three electronic boards with specific tasks directly connected to groups of 2 or 3 sensors. The core of the readout is composed of MAROC3 and FPGA chips. The MAROC3 chip is able to discriminate the 64 signals from one MAPMT and to produce 64 corresponding binary outputs with 100% efficiency starting at a small fraction of the single-photon signal, while the FPGA chip provides 1 ns TDC capability with 8 μs maximum latency and acts as a DAQ controller. The system is designed to be almost dead-time free at the foreseen 20 kHz CLAS12 trigger rate. The best working conditions for single-photon detection have been studied at laser stands, test beams, and with the JLab electron beam data. A report of the photon detector preparation, commissioning and operation is here discussed.
•Single-photon detection with cutting-edge multi-anode and silicon photo-sensors.•Tessellated readout system for single-photon detection at sub-cm spatial resolution.•Flexible architecture for easily adaptation to various sensors, geometries and setups.•100% efficient discrimination capability down to few fC single-photon signals.•Almost dead-time free parallel digitalization with better then 1 ns time resolution.
A measurement of the CP-violating observables from B -> (DK +/-)-K-* and B-+/- -> D-*pi(+/-) decays is presented, where D-*(D) is an admixture of D-*0 and D-0 (D-0 and (0)) states and is ...reconstructed through the decay chains D-*-> D pi(0)/gamma and D -> KS0 pi+pi-/KS0K+K-. The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb(-1) at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle gamma is determined to be (69(-14)(+13))degrees using the measured CP-violating observables. The hadronic parameters r(B)(D)*(K +/-),r(B)(D)*(pi +/-),delta(D)(B)*(K +/-),delta(D)(B)*(pi +/-), which are the ratios and strong phase differences between favoured and suppressed B-+/- decays, are also reported.
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb(-1) collected with the LHCb detector, seven decay modes of the B-C(+) meson into a J/psi or psi(2S) meson and ...three charged hadrons, kaons or pions, are studied. The decays B-C (+)-> (psi(2S) -> J/psi pi(+)pi(-))pi(+), B+C -> (psi(2S)pi(+)pi(-)pi(+), B+C -> J/psi K+pi(-)pi(+) and B+C -> J/K+K-K+ are observed for the first time, and evidence for the B-C (+)-> (psi(2S)K+K-pi(+), decay is found, where J/psi and psi(2S) mesons are reconstructed in their dimuon decay modes. The ratios of branching fractions between the different B-C(+) decays are reported as well as the fractions of the decays proceeding via intermediate resonances. The results largely support the factorisation approach used for a theoretical description of the studied decays.
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D
D
π
mass spectrum just below the D
D
mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar Formula: see text tetraquark with a quark content of Formula: see text and spin-parity quantum numbers J
= 1
. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D
mesons is consistent with the observed D
π
mass distribution. To analyse the mass of the resonance and its coupling to the D
D system, a dedicated model is developed under the assumption of an isoscalar axial-vector Formula: see text state decaying to the D
D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the Formula: see text state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
Search for the decay B 0 → ϕμ + μ Aaij, R.; Eklund, Lars; Zunica, G.
The journal of high energy physics,
05/2022, Letnik:
2022, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A search for the decay B-0 -> phi mu(+) mu(-) is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an ...integrated luminosity of 9 fb(-1). No evidence for the B-0 -> phi mu(+) mu(-) decay is found and an upper limit on the branching fraction, excluding the 0 and charmonium regions in the dimuon spectrum, of 4.4 x 10(-3) at a 90% credibility level, relative to that of the B-s(0) -> phi mu(+) mu(-) decay, is established. Using the measured B-s(0) -> phi mu(+) mu(-) branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B-0 -> phi mu(+) mu(-) in the full q(2) range is determined to be less than 3.2 x 10(-9) at a 90% credibility level.
A
bstract
The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at ...a centre-of-mass energy of
$$ \sqrt{s} $$
s
= 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5
.
4 nb
−
1
. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges
p
T
∈ 80
,
10 000) MeV
/c
and
η
∈ 2
.
0
,
4
.
8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
Single photon detection with the multi-anode CLAS12 RICH detector Contalbrigo, M.; Aaron, E.; Balossino, I. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2019, Letnik:
952, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Recently, the first module of the hybrid-optics large-area CLAS12 RICH at JLab has been put into operation using for the first time the well known Hamamatsu H8500 MAPMT and the new single-photon ...dedicated H12700, for a total of about 400 MAPMTs and 25000 pixels. The photon detector must efficiently detect single photons in the visible and near-UV light region, provide a fast response for background rejection and pattern recognition, and have a spatial resolution of less than 1 cm over an area of ≈1 m2. Each front-end readout unit is composed of three electronic boards with specific tasks directly connected to groups of 2 or 3 sensors. The core of the readout is composed of MAROC3 and FPGA chips. The MAROC3 chip is able to discriminate the 64 signals from one MAPMT and to produce 64 corresponding binary outputs with 100% efficiency starting at a small fraction of the single-photon signal, while the FPGA chip provides 1 ns TDC capability with 8 μs maximum latency and acts as a DAQ controller. The system is created to be almost dead-time free at the foreseen 20 kHz CLAS12 trigger rate. The best working conditions for single-photon detection have been studied at laser stands, test beams, and with the JLab electron beam data. A report of the photon detector preparation, commissioning and operation is here discussed.
A
bstract
This article presents differential measurements of the asymmetry between
$$ {\varLambda}_b^0 $$
Λ
b
0
and
$$ {\overline{\varLambda}}_b^0 $$
Λ
¯
b
0
baryon production rates in proton-proton ...collisions at centre-of-mass energies of
$$ \sqrt{s} $$
s
= 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb
−
1
. The
$$ {\varLambda}_b^0 $$
Λ
b
0
baryons are reconstructed through the inclusive semileptonic decay
$$ {\varLambda}_b^0 $$
Λ
b
0
→
$$ {\varLambda}_c^{+} $$
Λ
c
+
μ
−
$$ \overline{\nu} $$
ν
¯
μ
X
. The production asymmetry is measured both in intervals of rapidity in the range 2
.
15
< y <
4
.
10 and transverse momentum in 2
< p
T
<
27 GeV/
c
. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both
$$ \sqrt{s} $$
s
= 7 and 8 TeV data, assuming no
CP
violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in P
ythia
and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in
b
-hadron production at LHC energies.
Abstract The Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, ...corresponding to an integrated luminosity of 5.3 fb −1. Using the B 0 → D + D − K S 0 $$ {D}^{+}{D}^{-}{K}_S^0 $$ decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be R = σ Λ b 0 σ B 0 = B Λ b 0 → D + D − Λ B B 0 → D + D − K S 0 = 0.179 ± 0.022 ± 0.014 , $$ \mathcal{R}=\frac{\sigma_{\Lambda_b^0}}{\sigma_{B^0}}=\frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)}{\mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right)}=0.179\pm 0.022\pm 0.014, $$ where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel, B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ , and the cross-section ratio, σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , previously measured by LHCb are used to derive the branching fraction of the Λ b 0 $$ {\Lambda}_b^0 $$ → D + D − Λ decay B Λ b 0 → D + D − Λ = 1.24 ± 0.15 ± 0.10 ± 0.28 ± 0.11 × 10 − 4 , $$ \mathcal{B}\left({\Lambda}_b^0\to {D}^{+}{D}^{-}\Lambda \right)=\left(1.24\pm 0.15\pm 0.10\pm 0.28\pm 0.11\right)\times {10}^{-4}, $$ where the third and fourth contributions are due to uncertainties of B B 0 → D + D − K S 0 $$ \mathcal{B}\left({B}^0\to {D}^{+}{D}^{-}{K}_{\textrm{S}}^0\right) $$ and σ Λ b 0 / σ B 0 $$ {\sigma}_{\Lambda_b^0}/{\sigma}_{B^0} $$ , respectively. Inspection of the D +Λ and D + D − invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The Λ b 0 $$ {\Lambda}_b^0 $$ → D *+ D − Λ decay is also observed for the first time as a partially reconstructed component in the D + D − Λ invariant mass spectrum.
Abstract A search for the fully reconstructed B s 0 $$ {B}_s^0 $$ → μ + μ − γ decay is performed at the LHCb experiment using proton-proton collisions at s $$ \sqrt{s} $$ = 13 TeV corresponding to an ...integrated luminosity of 5.4 fb −1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 2 m μ 1.70 GeV / c 2 , B B s 0 → μ + μ − γ < 7.7 × 10 − 8 , m μ + μ − ∈ 1.70, 2.88 GeV / c 2 , B B s 0 → μ + μ − γ < 4.2 × 10 − 8 , m μ + μ − ∈ 3.92 m B s 0 GeV / c 2 , $$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left2{m}_{\mu },1.70\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left\textrm{1.70,2.88}\right\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left3.92,{m}_{B_s^0}\right\textrm{GeV}/{c}^2,\end{array}} $$ at 95% confidence level. Additionally, upper limits are set on the branching fraction in the 2m μ , 1.70 GeV/c 2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals.
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