The production of
(1
),
(2
) and
(3
) mesons in proton-proton collisions at the centre-of-mass energy of Formula: see text is studied with the LHCb detector. The analysis is based on a data sample of ...25 pb
collected at the Large Hadron Collider. The
mesons are reconstructed in the decay mode
→
and the signal yields are extracted from a fit to the
invariant mass distributions. The differential production cross-sections times dimuon branching fractions are measured as a function of the
transverse momentum
and rapidity
, over the range
<15 GeV/c and 2.0<
<4.5. The cross-sections times branching fractions, integrated over these kinematic ranges, are measured to be Formula: see text where the first uncertainty is statistical, the second systematic and the third is due to the unknown polarisation of the three
states.
A
bstract
A search for the lepton-flavour violating decays
B
s
0
→
e
±
μ
∓
and
B
0
→
e
±
μ
∓
is performed based on a sample of proton-proton collision data corresponding to an integrated ...luminosity of 3 fb
−1
, collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the
B
s
0
→
e
±
μ
∓
decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate. The results are
@
@
ℬ
B
s
0
→
e
±
μ
∓
<
6.3
5.4
×
1
0
−
9
and
@
@
ℬ
B
s
0
→
e
±
μ
∓
<
7.2
6.0
×
1
0
−
9
at 95% (90%) confidence level, respectively. The upper limit on the branching fraction of the
B
0
→
e
±
μ
∓
decay is also evaluated, obtaining
@
@
ℬ
B
0
→
e
±
μ
∓
<
1.3
1.0
×
1
0
−
9
at 95% (90%) confidence level. These are the strongest limits on these decays to date.
The charged-particle production ratios
,
K
−
/
K
+
,
π
−
/
π
+
,
, (
K
+
+
K
−
)/(
π
+
+
π
−
) and
are measured with the LHCb detector using 0.3 nb
−1
of
pp
collisions delivered by the LHC at
and ...1.8 nb
−1
at
. The measurements are performed as a function of transverse momentum
p
T
and pseudorapidity
η
. The production ratios are compared to the predictions of several Monte Carlo generator settings, none of which are able to describe adequately all observables. The ratio
is also considered as a function of rapidity loss, Δ
y
≡
y
beam
−
y
, and is used to constrain models of baryon transport.
Charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of
in different intervals of pseudorapidity
η
. Charged particles are ...reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the
η
ranges −2.5<
η
<−2.0 and 2.0<
η
<4.5. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/
c
a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of
η
. In general, the models underestimate charged particle production.
The possible role of folate supplementation in reducing hyperhomocysteinemia in dialysis patients has been reported in several recent papers. However, scant data are available for peritoneal dialysis ...patients; besides, none of these studies investigated either the role of intraerythrocyte folate concentration or the presence of side effects caused by folate administration. Sixty-six peritoneal dialysis patients with hyperhomocysteinemia (>15 micromol/l) and normal folate status (as assessed by erythrocyte folate level >600 nmol/l) were randomly allocated to receive either oral folate (5 mg/day) or no vitamin supplementation. After 2 months of therapy, patients were requested to answer a questionnaire investigating the occurrence of symptoms possibly related to folate supplementation. Twenty-nine treated patients and 30 untreated controls completed the study. In the treated patients, serum and erythrocyte folate increased significantly (p < 0.0001) (respectively from 10.6 +/- 4.9 to 237 +/- 231 nmol/l and from 1,201 +/- 297 to 2,881 +/- 294 nmol/l) to levels at the uppermost limit of detection by laboratory methods. Serum vitamin B(12) levels did not change. Plasma homocysteine levels decreased from 54 +/- 32 to 23 +/- 14 micromol/l after folate supplementation and remained unchanged in the control group. After 4 months of folate therapy, homocysteine concentration was within the normal range in 5 patients (17%) and below 30 micromol/l in the other 21 (72%). Folate therapy resulted in a decrease in homocysteine of more than 50% in 45% of the patients and decrease of more than 20% in a further 38%. No significant symptoms were reported. Thus, serum and erythrocyte folate increase confirms that normal folate levels are inadequate in dialysis patients, even if serum and erythrocyte levels before folate supplementation cannot predict the effect on homocysteine plasma levels.
A binned Dalitz plot analysis of B± → DK± decays, with D → KS0π+π− and D → KS0K+K−, is used to perform a measurement of the CP-violating observables x± and y±, which are sensitive to the ...Cabibbo-Kobayashi-Maskawa angle γ. The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb−1, the values of the CP violation parameters are found to be x− = (9.0 ± 1.7 ± 0.7 ± 0.4) × 10−2, y− = (2.1 ± 2.2 ± 0.5 ± 1.1) × 10−2, x+ = (−7.7 ± 1.9 ± 0.7 ± 0.4) × 10−2, and y+ = (−1.0 ± 1.9 ± 0.4 ± 0.9) × 10−2. The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty (on the strong-phase measurements. These values are used to obtain γ = (87− 12+ 11)∘, rB = 0.086− 0.014+ 0.013, and δB = (101±11)°, where rB is the ratio between the suppressed and favoured B-decay amplitudes and δB is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give γ = (80− 9+ 10)∘, rB = 0.080 ± 0.011, and δB = (110 ± 10)°.
A search is performed for the central exclusive production of pairs of charmonia produced in proton-proton collisions. Using data corresponding to an integrated luminosity of collected at ...centre-of-mass energies of 7 and 8 TeV, and pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges and . Searches are also performed for pairs of P-wave charmonia and limits are set on their production. The cross-sections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be where the upper limits are set at the 90% confidence level. The measured and cross-sections are consistent with theoretical expectations.
Exclusive J ψ and ψ(2S) vector meson production has been observed in the dimuon channel using the LHCb detector. The cross-section times branching fractions to two muons with pseudorapidities between ...2.0 and 4.5 are measured to be where the first uncertainties are statistical and the second are systematic. The measurements are found to be in good agreement with results from previous experiments and theoretical predictions. The J ψ photoproduction cross-section has been measured as a function of the photon-proton centre-of-mass energy. The results are consistent with measurements obtained at HERA and confirm a similar power law behaviour for the photoproduction cross-section.
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