A
bstract
The isospin asymmetries of
B
→
Kμ
+
μ
−
and
B
→
K
*
μ
+
μ
−
decays and the partial branching fractions of the
B
0
→
K
0
μ
+
μ
−
,
B
+
→
K
+
μ
+
μ
−
and
B
+
→
K
*+
μ
+
μ
−
decays are ...measured as functions of the dimuon mass squared,
q
2
. The data used correspond to an integrated luminosity of 3 fb
−1
from proton-proton collisions collected with the LHCb detector at centre-of-mass energies of 7 TeV and 8 TeV in 2011 and 2012, respectively. The isospin asymmetries are both consistent with the Standard Model expectations. The three measured branching fractions favour lower values than their respective theoretical predictions, however they are all individually consistent with the Standard Model.
Angular analysis of the rare decay Bs0→ ϕμ+μ Ackernley, T.; Balagura, V.; Belyaev, I. ...
The journal of high energy physics,
11/2021, Letnik:
2021, Številka:
11
Journal Article
Recenzirano
Odprti dostop
A
bstract
An angular analysis of the rare decay
B
s
0
→ ϕμ
+
μ
−
is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, ...corresponding to an integrated luminosity of 8.4 fb
−
1
. The observables describing the angular distributions of the decay
B
s
0
→ ϕμ
+
μ
−
are determined in regions of
q
2
, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.
Resonant structures in B^{0}→ψ^{'}π^{-}K^{+} decays are analyzed by performing a four-dimensional fit of the decay amplitude, using pp collision data corresponding to 3 fb^{-1} collected with the ...LHCb detector. The data cannot be described with K^{+}π^{-} resonances alone, which is confirmed with a model-independent approach. A highly significant Z(4430)^{-}→ψ^{'}π^{-} component is required, thus confirming the existence of this state. The observed evolution of the Z(4430)^{-} amplitude with the ψ^{'}π^{-} mass establishes the resonant nature of this particle. The mass and width measurements are substantially improved. The spin parity is determined unambiguously to be 1^{+}.
The Ξ_{c}^{+}K^{-} mass spectrum is studied with a sample of pp collision data corresponding to an integrated luminosity of 3.3 fb^{-1}, collected by the LHCb experiment. The Ξ_{c}^{+} is ...reconstructed in the decay mode pK^{-}π^{+}. Five new, narrow excited Ω_{c}^{0} states are observed: the Ω_{c}(3000)^{0}, Ω_{c}(3050)^{0}, Ω_{c}(3066)^{0}, Ω_{c}(3090)^{0}, and Ω_{c}(3119)^{0}. Measurements of their masses and widths are reported.
A combined amplitude analysis is performed for the decays B^{0}→Dover ¯^{0}D_{s}^{+}π^{-} and B^{+}→D^{-}D_{s}^{+}π^{+}, which are related by isospin symmetry. The analysis is based on data collected ...by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb^{-1}. Two new resonant states with masses of 2.908±0.011±0.020 GeV and widths of 0.136±0.023±0.013 GeV are observed, which decay to D_{s}^{+}π^{+} and D_{s}^{+}π^{-} respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content csover ¯udover ¯, and the latter state is a neutral tetraquark composed of csover ¯uover ¯d quarks. Both states are found to have spin-parity of 0^{+}, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.
The quantum numbers of the X(3872) meson are determined to be J(PC)=1(++) based on angular correlations in B(+)→X(3872)K(+) decays, where X(3872)→π(+)π(-)J/ψ and J/ψ→μ(+)μ(-). The data correspond to ...1.0 fb(-1) of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements J(PC)=2(-+) is rejected with a confidence level equivalent to more than 8 Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
Simulation of 3D-Silicon sensors for the TIMESPOT project Loi, A.; Lai, A.; Dalla Betta, G.F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2019, Letnik:
936
Journal Article
Recenzirano
The experimental conditions in future High Luminosity LHC experiments require new detector systems with increased performances compared to the current state of the art. In this context, increasing ...spacial resolution and including time measurement with a resolution of less than 50 ps for particle tracking systems can avoid false track reconstruction due to event pile up. For this kind of future tracking detectors the 3D silicon sensor technology appears as a good option. In this context the TIMESPOT initiative was launched. Concerning the development of the sensor, different geometrical solutions have been explored and simulated to optimize the timing response of the single pixel sensor using Sentaurus TCAD. The configuration with the best electric field characteristics for timing was selected for signal simulation. In order to compensate the very time-consuming behavior of TCAD simulations, a faster charge transport simulator with TCAD and Geant4 support is under development. Further sensor configurations, including a first primitive capacitive and resistive load, were also simulated and evaluated. This paper shows a general overview of the project with particular attention to the silicon sensor development. First results are presented.
Observations are reported of different sources of CP violation from an amplitude analysis of B^{+}→π^{+}π^{+}π^{-} decays, based on a data sample corresponding to an integrated luminosity of 3 ...fb^{-1} of pp collisions recorded with the LHCb detector. A large CP asymmetry is observed in the decay amplitude involving the tensor f_{2}(1270) resonance, and in addition significant CP violation is found in the π^{+}π^{-}S wave at low invariant mass. The presence of CP violation related to interference between the π^{+}π^{-}S wave and the P wave B^{+}→ρ(770)^{0}π^{+} amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into CP -violation effects in hadronic B decays.
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