Search for the rare decay KS→μ+μ Abellan Beteta, Carlos; Calvo Gómez, Míriam; Camboni, Alessandro ...
The journal of high energy physics,
01/2013
Journal Article
Recenzirano
Odprti dostop
A search for the decay K0S→μ+μ− is performed, based on a data sample of 1.0 fb−1 of pp collisions at s√=7TeV collected by the LHCb experiment at the Large Hadron Collider. The observed number of ...candidates is consistent with the background-only hypothesis, yielding an upper limit of B(K0S→μ+μ−) < 11(9) × 10−9 at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement.
A search is performed for the as yet unobserved baryonic Λb→Λη′ and Λb→Λη decays with 3fb−1 of proton-proton collision data recorded by the LHCb experiment. The B0→K0Sη′ decay is used as a ...normalisation channel. No significant signal is observed for the Λb→Λη′ decay. An upper limit is found on the branching fraction of B(Λb→Λη′)<3.1×10−6} at 90\% confidence level. Evidence is seen for the presence of the Λb→Λη decay at the level of 3σ significance, with a branching fraction B(Λb→Λη)=(9.3+7.3−5.3)×10−6}.
A
bstract
The relative production rate of
$ B_s^0 $
and
B
0
mesons is determined with the hadronic decays
$ B_s^0\to D_s^{-}{\pi^{+}} $
and
B
0
→
D
−
K
+
. The measurement uses data corresponding to ...1.0 fb
−1
of
pp
collisions at a centre-of-mass energy of
$ \sqrt{s}=7 $
TeV recorded in the forward region with the LHCb experiment. The ratio of production rates,
f
s
/f
d
, is measured to be 0
.
238 ± 0
.
004 ± 0
.
015 ± 0
.
021, where the first uncertainty is statistical, the second systematic, and the third theoretical. This is combined with a previous LHCb measurement to obtain
f
s
/f
d
= 0
.
256 ± 0
.
020. The dependence of
f
s
/f
d
on the transverse momentum and pseudorapidity of the
B
meson is determined using the decays
$ B_s^0\to D_s^{-}{\pi^{+}} $
and
B
0
→
D
−
π
+
. There is evidence for a decrease with increasing transverse momentum, whereas the ratio remains constant as a function of pseudorapidity. In addition, the ratio of branching fractions of the decays
B
0
→
D
−
K
+
and
B
0
→
D
−
π
+
is measured to be 0
.
0822 ± 0
.
0011 (stat) ± 0
.
0025 (syst).
Using a data set corresponding to an integrated luminosity of 3fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the ...B0s→J/ψη decay mode, τeff, is measured to be τeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the lifetime of the light B0s mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.
The cross-section for inclusive ϕ meson production in pp collisions at a centre-of-mass energy of s=7 TeV has been measured with the LHCb detector at the Large Hadron Collider. The differential ...cross-section is measured as a function of the ϕ transverse momentum pT and rapidity y in the region 0.6<pT<5.0 GeV/c and 2.44<y<4.06. The cross-section for inclusive ϕ production in this kinematic range is σ(pp→ϕX)=1758±19(stat)−14+43(syst)±182(scale) μb, where the first systematic uncertainty depends on the pT and y region and the second is related to the overall scale. Predictions based on the Pythia 6.4 generator underestimate the cross-section.
Measurements of the differential branching fraction and angular moments of the decay B0→K+π−μ+μ− in the K∗0,2(1430)0 in the K+π− invariant mass range 1330<m(K+π−)<1530 MeV/c2 are presented. ...Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb−1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q2, between 0.1 and 8.0 GeV2/c4. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q2 range 1.1--6.0 GeV2/c4.
The charged-particle production ratios p¯/p, K −/K +, π −/π +, (p+p¯)/(π++π−), (K ++K −)/(π ++π −) and (p+p¯)/(K++K−) are measured with the LHCb detector using 0.3 nb−1 of pp collisions delivered by ...the LHC at s√=0.9 TeV and 1.8 nb−1 at s√=7 TeV. 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 p¯/p is also considered as a function of rapidity loss, Δy≡y beam−y, and is used to constrain models of baryon transport.
PDF
