The branching fraction of the rare decay Lambda(0 )(b)-> Lambda(1520)mu(+)mu(-) is measured for the first time, in the squared dimuon mass intervals q(2), excluding the J/psi and psi(2S) regions. ...The data sample analyzed was collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb(-1). The result in the highest q(2) interval, q(2) > 15.0 GeV2/c(4), where theoretical predictions have the smallest model dependence, agrees with the predictions.
A measurement of charm mixing and CP-violating parameters is reported, using B over bar -> D0(-> K0S pi+pi-)x mu- nu over bar mu X decays reconstructed in proton-proton collisions collected by ...the LHCb experiment during the years 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. The measured mixing and CP-violating parameters are xCP = 4.29 1 1.48(stat) 1 0.26(syst) x 10-3, yCP = 12.61 1 3.12(stat) 1 0.83(syst) x 10-3, Ax = -0.77 1 0.93(stat) 1 0.28(syst) x 10-3, Ay = 3.01 1 1.92(stat) 1 0.26(syst) x 10-3. The results are complementary to and consistent with previous measurements. A combination with the recent LHCb analysis of D*+ -> D0(-> K0S pi+ pi-)pi+ decays is reported.
The decay B- -> Lambda(+)(c)(Lambda) over bar K--(c)- is studied in proton-proton collisions at a center-of-mass energy of root s = 13 TeV using data corresponding to an integrated luminosity of 5 ...fb(-1) collected by the LHCb experiment. In the Lambda K-+(c)- system, the Xi(c)(2930)(0) state observed at the BABAR and Belle experiments is resolved into two narrower states, Xi(c)(2923)(0) and Xi(c)(2939)(0), whose masses and widths are measured to be m(Xi(c)(2930)(0) = 2924.5 +/- 0.4 +/- 1.1 Mev, m Xi(c)(2930)(0)) = 2938.5 +/- 0.9 +/- 2.3 Mev, Gamma(Xi(c)(2930)(0)) = 4.8 +/- 0.9 +/- 1.5 MeV, Gamma(Xi(c)(2930)(0) - 11.0 +/- 1.9 +/- 7.5 MeV, where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt Lambda K-+(c)- sample. Evidence of a new Xi(c)(2930)(0) state is found with a local significance of 3.8 sigma, whose mass and width are measured to be 2881.8 +/- 3.1 +/- 8.5 MeV and 12.4 +/- 5.3 +/- 5.8 MeV, respectively. In addition, evidence of a new decay mode Xi(c)(2930)(0) -> Lambda K-+(c) is found with a significance of 3.7 sigma. The relative branching fraction of B- -> Lambda(+)(c)(Lambda) over bar K--(c)- with respect to the B- -> D+D-K- decay is measured to be 2.36 +/- 0.11 +/- 0.22 +/- 0.25, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.
A study of the B+ -> (KSK+)-K-0 K-pi(+) and B+ -> (KSK+K+)-K-0 pi(-) decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The ...(KSK)-K-0 pi invariant mass spectra from both decay modes reveal a rich content of charmonium resonances. New precise measurements of the eta(c) and eta(c)(2S) resonance parameters are performed and branching fraction measurements are obtained for B+ decays to eta(c), J/psi, eta(c)(2S) and chi(c1) resonances. In particular, the first observation and branching fraction measurement of B+ -> chi K-c0(0)pi(+) is reported as well as first measurements of the B+ -> (KK+K-)-K-0 pi(+) and B+ -> (KK+K+)-K-0 pi(-) branching fractions. Dalitz plot analyses of eta(c) -> (KSK)-K-0 pi and eta(c)(2S) -> (KSK)-K-0 pi decays are performed. A new measurement of the amplitude and phase of the K pi S-wave as functions of the K pi mass is performed, together with measurements of the K-0*(1430), K-0*(1950) and a(0)(1700) parameters. Finally, the branching fractions of chi(c1) decays to K* resonances are also measured.
We studied the efficacy of tonsillectomy, or tonsillectomy with adenoidectomy, in 187 children severely affected with recurrent throat infection. Ninety-one of the children were assigned randomly to ...either surgical or nonsurgical treatment groups, and 96 were assigned according to parental preference. In both the randomized and nonrandomized trials, the effects of tonsillectomy and of tonsillectomy with adenoidectomy were similar. By various measures, the incidence of throat infection during the first two years of follow-up was significantly lower (P less than or equal to 0.05) in the surgical groups than in the corresponding nonsurgical groups. Third-year differences, although in most cases not significant, also consistently favored the surgical groups. On the other hand, in each follow-up year many subjects in the nonsurgical groups had fewer than three episodes of infection, and most episodes among subjects in the nonsurgical groups were mild. Of the 95 subjects treated with surgery, 13 (14 per cent) had surgery-related complications, all of which were readily managed or self-limited. These results warrant the election of tonsillectomy for children meeting the trials' stringent eligibility criteria, but also provide support for nonsurgical management. Treatment for such children must therefore be individualized.
A
bstract
This article presents differential measurements of the asymmetry between
Λ
b
0
and
Λ
¯
b
0
baryon production rates in proton-proton collisions at centre-of-mass energies of
s
= 7 and 8 TeV ...collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb
−
1
. The
Λ
b
0
baryons are reconstructed through the inclusive semileptonic decay
Λ
b
0
→
Λ
c
+
μ
−
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
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.
A
bstract
A data set corresponding to an integrated luminosity of 9 fb
−
1
of proton-proton collisions collected by the LHCb experiment has been analysed to search for
B
c
+
→
D
s
∗
+
—
D
∗
0
decays. ...The decays are fully or partially reconstructed, where one or two missing neutral pions or photons from the decay of an excited charm meson are allowed. Upper limits for the branching fractions, normalised to
B
+
decays to final states with similar topologies, are obtained for sixteen
B
c
+
decay modes. For the decay
B
c
+
→
D
s
+
D
¯
0
, an excess with a significance of 3.4 standard deviations is found.
A
bstract
The inclusive
b
b
¯
- and
c
c
¯
-dijet production cross-sections in the forward region of
pp
collisions are measured using a data sample collected with the LHCb detector at a centre-of-mass ...energy of 13 TeV in 2016. The data sample corresponds to an integrated luminosity of 1.6 fb
−
1
. Differential cross-sections are measured as a function of the transverse momentum and of the pseudorapidity of the leading jet, of the rapidity difference between the jets, and of the dijet invariant mass. A fiducial region for the measurement is defined by requiring that the two jets originating from the two
b
or
c
quarks are emitted with transverse momentum greater than 20 GeV/
c
, pseudorapidity in the range 2
.
2
< η <
4
.
2, and with a difference in the azimuthal angle between the two jets greater than 1.5. The integrated
b
b
¯
-dijet cross-section is measured to be 53
.
0 ± 9
.
7 nb, and the total
c
c
¯
-dijet cross-section is measured to be 73 ± 16 nb. The ratio between
c
c
¯
- and
b
b
¯
-dijet cross-sections is also measured and found to be 1
.
37 ± 0
.
27. The results are in agreement with theoretical predictions at next-to-leading order.
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