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 D-(s)(()*())+ ((D) over bar)(*)0 decays. ...The decays are fully or partially reconstructed, where one or two (8) 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) over bar (0), an excess with a significance of 3.4 standard deviations is found.
Observation of new excited $${B} ^0_{s} $$ states Aiola, S.; Albero, A. Alfonso; Artamonov, A. ...
The European physical journal. C, Particles and fields,
07/2021, Letnik:
81, Številka:
7
Journal Article
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Abstract
A structure is observed in the
$${B} ^{\pm }{K} ^{\mp }$$
B
±
K
∓
mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the ...LHCb detector and corresponding to a total integrated luminosity of 9
$$\,\text {fb} ^{-1}$$
fb
-
1
. The structure is interpreted as the result of overlapping excited
$${B} ^0_{s} $$
B
s
0
states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to
$${B} ^{\pm }{K} ^{\mp }$$
B
±
K
∓
, are determined to be
$$\begin{aligned} m_1&= 6063.5 \pm 1.2 \text { (stat)} \pm 0.8\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _1&= 26 \pm 4 \text { (stat)} \pm 4\text { (syst)}\,\text {Me}\text {V}, \\ m_2&= 6114 \pm 3 \text { (stat)} \pm 5\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _2&= 66 \pm 18 \text { (stat)} \pm 21\text { (syst)}\,\text {Me}\text {V}. \end{aligned}$$
m
1
=
6063.5
±
1.2
(stat)
±
0.8
(syst)
Me
,
Γ
1
=
26
±
4
(stat)
±
4
(syst)
Me
,
m
2
=
6114
±
3
(stat)
±
5
(syst)
Me
,
Γ
2
=
66
±
18
(stat)
±
21
(syst)
Me
.
Alternative values assuming a decay through
$${B} ^{*\pm }{K} ^{\mp }$$
B
∗
±
K
∓
, with a missing photon from the
$$B^{*\pm } \rightarrow B^{\pm }\gamma $$
B
∗
±
→
B
±
γ
decay, which are shifted by approximately 45
$$\,\text {Me}$$
Me
V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed
$$B_{s2}^{*0}$$
B
s
2
∗
0
state is determined to be
$$0.87 \pm 0.15 \text { (stat)} \pm 0.19 \text { (syst)}$$
0.87
±
0.15
(stat)
±
0.19
(syst)
.
A study of prompt charm-hadron pair production in proton-lead collisions at $\sqrt{s_{NN}$ = 8.16 TeV is performed using data corresponding to an integrated luminosity of about 30 nb-1 , collected ...with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.
A search is performed for heavy neutrinos in the decay of a
W
boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately
3.0
fb
-
1
of proton–proton ...collision data at centre-of-mass energies of 7 and
8
TeV
collected with the LHCb experiment. Both same-sign and opposite-sign muons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at
95
%
confidence level in the heavy-neutrino mass range from 5 to
50
GeV/
c
2
. These are of the order of
10
-
3
for lepton-number-conserving decays and of the order of
10
-
4
for lepton-number-violating heavy-neutrino decays.
The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon center-of-mass energy sqrts_{NN}=5 TeV is studied at LHCb as a function of ...pseudorapidity (η) and transverse momentum (p_{T}) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of η between -4.8<η<-2.5 (backward region) and 2.0<η<4.8 (forward region), and p_{T} between 0.2<p_{T}<8.0 GeV/c. The results show a suppression of charged particle production in proton-lead collisions relative to proton-proton collisions in the forward region and an enhancement in the backward region for p_{T} larger than 1.5 GeV/c. This measurement constrains nuclear PDFs and saturation models at previously unexplored values of the parton momentum fraction down to 10^{-6}.
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