478 research outputs found
Measurement of CP asymmetries in D s + → η π + and D s + → η ′ π + decays
No full textAbstract Searches for CP violation in the decays D s + → η π + and D s + → η ′ π + are performed using pp collision data corresponding to 6 fb −1 of integrated luminosity collected by the LHCb experiment. The calibration channels D s + → ϕ π + are used to remove production and detection asymmetries. The resulting CP-violating asymmetries are A CP = D + → η π + = 0.34 ± 0.66 ± 0.16 ± 0.05 % , A CP = D s + → η π + = 0.32 ± 0.51 ± 0.12 % , A CP = D + → η ′ π + = 0.49 ± 0.18 ± 0.06 ± 0.05 % , A CP = D s + → η ′ π + = 0.01 ± 0.12 ± 0.08 % , where the first uncertainty is statistical, the second is systematic and the third, relevant for the D + channels, is due to the uncertainty on A CP = D + → ϕ π + . These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of CP violation. A combination of these results with previous LHCb measurements is presented
Angular analysis of B0 → D∗−D∗+s with D∗+s → D+sγ decays
No full textThe first full angular analysis of the B0 → D∗−D∗+
s decay is performed using 6 fb−1 of pp collision data collected with the LHCb experiment at a centre-of-mass
energy of 13 TeV. The D∗+
s → D+
s γ and D∗− → D
0
π
− vector meson decays are used
with the subsequent D+
s → K+K−π
+ and D
0
→ K+π
− decays. All helicity amplitudes
and phases are measured, and the longitudinal polarisation fraction is determined to be
fL = 0.578±0.010±0.011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to
align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [B(B0 → D∗−D∗+
s
) × B(D∗+
s → D+
s γ)]/B(B0 → D∗−D+
s
) is measured to be
2.045 ± 0.022 ± 0.071 with world-best precision. In addition, the first observation of the
Cabibbo-suppressed Bs → D∗−D+
s decay is made with a significance of seven standard deviations. The branching fraction ratio B(Bs → D∗−D+
s
)/B(B0 → D∗−D+
s
) is measured to
be 0.049 ± 0.006 ± 0.003 ± 0.002, where the third uncertainty is due to limited knowledge
of the ratio of fragmentation fractions
Measurement of Υ production in pp collisions at s = 5 TeV
No full textAbstract The production cross-sections of Υ mesons, namely Υ(1S), Υ(2S) and Υ(3S), in pp collisions at s = 5 TeV are measured with a data sample corresponding to an integrated luminosity of 9.13 ± 0.18 pb −1 collected by the LHCb detector. The Υ mesons are reconstructed in the decay mode Υ → μ + μ − . Double differential cross-sections times branching fractions, as functions of the transverse momentum p T and the rapidity y of the Υ mesons, are measured in the range p T < 20 GeV/c and 2.0 < y < 4.5. The results integrated over these p T and y ranges are σ Υ 1 S × B Υ 1 S → μ + μ − = 2101 ± 33 ± 83 pb , σ Υ 2 S × B Υ 2 S → μ + μ − = 526 ± 20 ± 21 pb , σ Υ 3 S × B Υ 3 S → μ + μ − = 242 ± 16 ± 10 pb , where the first uncertainties are statistical and the second are systematic. The ratios of cross-sections between measurements of two different Υ states and between measurements at different centre-of-mass energies are determined. The nuclear modification factor of Υ(1S) at s = 5 TeV is updated as well using the directly measured cross-section results from this analysis
Measurement of CP asymmetries in D(s)+→ηπ+ and D(s)+→η′π+ decays
No full textSearches for CP violation in the decays D(s)+→ηπ+ and D(s)+→η′π+ are performed using pp collision data corresponding to 6 fb−1 of integrated luminosity collected by the LHCb experiment. The calibration channels D(s)+→φπ+ are used to remove production and detection asymmetries. The resulting CP-violating asymmetries areACP=(D+→ηπ+)=(0.34±0.66±0.16±0.05)%,ACP=(Ds+→ηπ+)=(0.32±0.51±0.12)%,ACP=(D+→η′π+)=(0.49±0.18±0.06±0.05)%,ACP=(Ds+→η′π+)=(0.01±0.12±0.08)%, where the first uncertainty is statistical, the second is systematic and the third, relevant for the D+ channels, is due to the uncertainty on ACP= (D+→ φπ+). These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of CP violation. A combination of these results with previous LHCb measurements is presented. [Figure not available: see fulltext.]
Measurement of CP asymmetries in D+(s) → ηπ+ and D+(s) → η′π+ decays
No full textSearches for CP violation in the decays D-(s)(+) -> eta pi(+) and D-(s)(+) -> eta'pi(+) are performed using pp collision data corresponding to 6 fb(-1) of integrated luminosity collected by the LHCb experiment. The calibration channels D-(s)(+) -> phi pi(+) are used to remove production and detection asymmetries. The resulting CP-violating asymmetries are
A(CP) (D+ -> eta pi(+)) = (0.34 +/- 0.66 +/- 0.16 +/- 0.05)%,
A(CP) (D-s(+) -> eta pi(+)) = (0.32 +/- 0.51 +/- 0.12)%,
A(CP) (D+ -> eta'pi(+)) = (0.49 +/- 0.18 +/- 0.06 +/- 0.05)%,
A(CP) (D-s(+) -> eta'pi(+)) = (0.01 +/- 0.12 +/- 0.08)%,
where the first uncertainty is statistical, the second is systematic and the third, relevant for the D+ channels, is due to the uncertainty on A(CP) (D+ -> phi pi(+)). These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of CP violation. A combination of these results with previous LHCb measurements is presented
Heterostructure Active Area Optimization by Simulation
No full textChanging LED performance characteristics, depending on Indium atoms concentration and at different
temperatures were simulated. It was suggested that a LED having p-n junction area S0 can be considered
as a sum of “SmallLEDs (SLEDs)” electrically connected in parallel, each SLED has its own In-content and
its own p-n junction area S(X). Good correlation in simulation and experimental results has been obtained.
It was determined that the best structure for AlGaInN NH is p+GaN / p+Al0.2Ga0.8N / 4(n-InxGa1 – xN-n-
GaN) / n+GaN. The main thing is that in the NH AA there are 4QW-in two central ones there is maximum
radiation and two ones at the both ends of active region are “barriers” which help to concentrate electrons
/ holes in active region and additionally “protect” QW from different defects
Search for CP violation in D(s)+→h+π0 and D(s)+→h+η decays
No full textSearches for CP violation in the two-body decays D-(s)(+) -> h(+)pi(0) and D-(s)(+) -> h(+)eta (where h(+) denotes a pi(+) or K+ meson) are performed using pp collision data collected by the LHCb experiment corresponding to either 9 fb(-1) or 6 fb(-1) of integrated luminosity. The pi(0) and eta mesons are reconstructed using the e(+) e(-)gamma final state, which can proceed as three-body decays pi(0) -> e(+) e(-) gamma and eta -> e(+) e(-)gamma, or via the two-body decays pi(0) -> gamma gamma and eta -> gamma gamma followed by a photon conversion. The measurements are made relative to the control modes D-(s)(+) K(S)(0)h(+) to cancel the production and detection asymmetries. The CP asymmetries are measured to be A(CP)(D+ -> pi(+)pi(0)) = (-1.3 +/- 0.9 +/- 0.6)%, A(CP)(D+ -> K+pi(0)) = (- 3.2 +/- 4.7 +/- 2.1)%, A(CP)(D+ -> pi(+)eta) = (-0.2 +/- 0.8 +/- 0.4)%, A(CP)(D+ -> K+eta) = (-6 +/- 10 +/- 4 )%, A(CP)(D-s(+) -> K+pi(0)) = (-0.8 +/- 3.9 +/- 1.2)%, A(CP)(D-s(+) -> pi(+)eta) = ( 0.8 +/- 0.7 +/- 0.5)%, A(CP)(D-s(+) -> K+eta) = ( 0.9 +/- 3.7 +/- 1.1)%, where the first uncertainties are statistical and the second systematic. These results are consistent with no CP violation and mostly constitute the most precise measurements of A(CP) in these decay modes to date
Search for CP violation in D-(s)(+) -> h(+) pi(0) and decays D-(s)(+) -> h(+) eta decays
No full textSearches for CP violation in the two-body decays D(s)+→h+π0 and D(s)+→h+η (where h+ denotes a π+ or K+ meson) are performed using pp collision data collected by the LHCb experiment corresponding to either 9 fb−1 or 6 fb−1 of integrated luminosity. The π0 and η mesons are reconstructed using the e+e−γ final state, which can proceed as three-body decays π0→ e+e−γ and η → e+e−γ, or via the two-body decays π0→ γγ and η → γγ followed by a photon conversion. The measurements are made relative to the control modes D(s)+→KS0h+ to cancel the production and detection asymmetries. The CP asymmetries are measured to beACP(D+→π+π0)=(−1.3±0.9±0.6)%,ACP(D+→K+π0)=(−3.2±4.7±2.1)%,ACP(D+→π+η)=(−0.2±0.8±0.4)%,ACP(D+→K+η)=(−6±10±4)%,ACP(Ds+→K+π0)=(−0.8±3.9±1.2)%,ACP(Ds+→π+η)=(0.8±0.7±0.5)%,ACP(Ds+→K+η)=(0.9±3.7±1.1)%, where the first uncertainties are statistical and the second systematic. These results are consistent with no CP violation and mostly constitute the most precise measurements of ACP in these decay modes to date. [Figure not available: see fulltext.
Measurement of the branching fraction of the decay
No full textA branching fraction measurement of the decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of fb. The branching fraction is found to be , where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the , and branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element . Additionally, the collision energy dependence of the hadronisation-fraction ratio is measured through and decays.A branching fraction measurement of the decay is presented using proton–proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of . The branching fraction is found to be , where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the , and branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo–Kobayashi–Maskawa matrix element . Additionally, the collision energy dependence of the hadronisation-fraction ratio is measured through and decays.A branching fraction measurement of the decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of fb. The branching fraction is found to be , where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the , and branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element . Additionally, the collision energy dependence of the hadronisation-fraction ratio is measured through and decays
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