904 research outputs found
Endozoochory by native and exotic herbivores in dry areas: consequences for germination and survival of Prosopis seeds
Mammalian herbivores can play a role in the endozoochorous dispersal of Prosopis seeds in the arid zones of Argentina, and the introduction of exotic mammals can change relevant parameters of the plant's reproductive ecology. Our specific goals were to quantify the seeds of Prosopis flexuosa, P. chilensis and P. torquata contained in the faeces of native [mara (Dolichotis patagonum), guanaco (Lama guanicoe)] and exotic [donkey (Equus asinus) and hare (Lepus europaeus)] mammals, and to determine the mortality, germination percentage and germination speed of seeds borne in faeces, compared with those collected from trees. In 2006, seeds were collected directly from trees or removed from mammal faeces. Seeds were counted and classified as apparently healthy or damaged. P. torquata and P. flexuosa seeds were found in the dung of guanaco, hare and mara, whereas only P. flexuosa seeds appeared in donkey faeces. P. chilensis seeds were only found in guanaco faeces. There was a notable relative abundance of seeds contained in small herbivore faeces in comparison to the large herbivores. The passage through the digestive tract of animals modified seed germination capacity and speed, with great variability between animal species. Guanacos had greater effects than donkeys on mortality, germination percentage and germination speed. Differences between the effects of both smaller-sized herbivores on seeds were much smaller.Fil: Campos, Claudia Monica. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Ăridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Ăridas; ArgentinaFil: Peco, Begoña. Universidad AutĂłnoma de Madrid; EspañaFil: Campos Valeria. Universidad Nacional de San Juan; ArgentinaFil: Malo ArrĂĄzola, Juan Esteban. Universidad AutĂłnoma de Madrid; EspañaFil: Giannoni, Stella Maris. Universidad Nacional de San Juan; ArgentinaFil: Suarez Francisco. Universidad AutĂłnoma de Madrid; Españ
Search for CP Violation in D-s(+) -> K-S(0)pi(+), D+ -> (KSK+)-K-0, and D+ -> phi pi(+) Decays
A search for charge-parity () violation in Cabibbo-suppressed , and decays is reported
using proton-proton collision data, corresponding to an integrated luminosity
of 3.8 fb, collected at a center-of-mass energy of 13 TeV with the LHCb
detector. High-yield samples of kinematically and topologically similar
Cabibbo-favored decays are analyzed to subtract nuisance
asymmetries due to production and detection effects, including those induced by
violation in the neutral kaon system. The results are \begin{align*}
\mathcal{A}_{CP}(D_s^+\to K_S^0 \pi^+)
&=\left(\phantom{-}1.3\phantom{0}\pm1.9\phantom{0}\pm0.5\phantom{0}\right)\times10^{-3},\\
\mathcal{A}_{CP}(D^+\to K_S^0 K^+)
&=\left(-0.09\pm0.65\pm0.48\right)\times10^{-3},\\ \mathcal{A}_{CP}(D^+\to \phi
\pi^+) &=\left(\phantom{-}0.05\pm0.42\pm0.29\right)\times10^{-3}, \end{align*}
where the first uncertainties are statistical and the second systematic. They
are the most precise measurements of these quantities to date, and are
consistent with symmetry.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-002.htm
Measurement of fs /fu Variation with Proton-Proton Collision Energy and B -Meson Kinematics
The ratio of the Bs0 and B+ fragmentation fractions fs and fu is studied with Bs0âJ/ÏÏ and B+âJ/ÏK+ decays using data collected by the LHCb experiment in proton-proton collisions at 7, 8, and 13 TeV center-of-mass energies. The analysis is performed in bins of B-meson momentum, longitudinal momentum, transverse momentum, pseudorapidity, and rapidity. The fragmentation-fraction ratio fs/fu is observed to depend on the B-meson transverse momentum with a significance of 6.0Ï. This dependency is driven by the 13 TeV sample (8.7Ï), while the results for the other collision energies are not significant when considered separately. Furthermore, the results show a 4.8Ï evidence for an increase of fs/fu as a function of collision energy
Observation of a narrow pentaquark state, P-c(4312)(+), and of the two-peak structure of the P-c(4450)(+)
A narrow pentaquark state, P-c(4312)(+), decaying to J/psi p, is discovered with a statistical significance of 7.3 sigma in a data sample of Lambda(0)(b) -> J/psi pK(-) decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P-c(4450)(+) pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P-c(4440)(+) and P-c(4457)(+), where the statistical significance of this two-peak interpretation is 5.4 sigma. The proximity of the Sigma(+)(c)(D) over bar (0) and Sigma(+)(c)(D) over bar (*0) thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states
Observation of the doubly charmed baryon decay Îcc++âÎcâČ+Ï+
The Îcc++âÎcâČ+Ï+ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fbâ1. The Îcc++âÎcâČ+Ï+ decay is reconstructed partially, where the photon from the ÎcâČ+âÎc+Îł decay is not reconstructed and the pKâÏ+ final state of the Îc+ baryon is employed. The Îcc++âÎcâČ+Ï+branching fraction relative to that of the Îcc++âÎc+Ï+ decay is measured to be 1.41 ± 0.17 ± 0.10, where the first uncertainty is statistical and the second systematic. [Figure not available: see fulltext.
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . The analysis uses beauty mesons produced in
proton-proton collisions collected with the LHCb detector between 2011 and
2018, corresponding to an integrated luminosity of 9 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
Study of charmonium and charmonium-like contributions in B+ â J/ÏηK+ decays
A study of B+â J/ÏηK+ decays, followed by J/Ï â ÎŒ+ÎŒâ and η â γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fbâ1. The J/Ïη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B+â (Ï2(3823) â J/Ïη)K+ and B+â (Ï(4040) â J/Ïη)K+ decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the Ï2(3823) â J/Ïη decay
Search for the lepton-flavor-violating decays Bs0âϱΌâ and B0âϱΌâ
Results are reported from a search for the rare decays
B
0
s
â
Ï
±
Ό
â
and
B
0
â
Ï
±
Ό
â
, where the
Ï
lepton is reconstructed in the channel
Ï
â
â
Ï
â
Ï
+
Ï
â
Μ
Ï
. These processes are effectively forbidden in the standard model, but they can potentially occur at detectable rates in models of new physics that can induce lepton-flavor-violating decays. The search is based on a data sample corresponding to
3
â
â
fb
â
1
of proton-proton collisions recorded by the LHCb experiment in 2011 and 2012. The event yields observed in the signal regions for both processes are consistent with the expected standard model backgrounds. Because of the limited mass resolution arising from the undetected
Ï
neutrino, the
B
0
s
and
B
0
signal regions are highly overlapping. Assuming no contribution from
B
0
â
Ï
±
Ό
â
, the upper limit
B
(
B
0
s
â
Ï
±
Ό
â
)
<
4.2
Ă
10
â
5
is obtained at 95% confidence level. If no contribution from
B
0
s
â
Ï
±
Ό
â
is assumed, a limit of
B
(
B
0
â
Ï
±
Ό
â
)
<
1.4
Ă
10
â
5
is obtained at 95% confidence level. These results represent the first limit on
B
(
B
0
s
â
Ï
±
Ό
â
)
and the most stringent limit on
B
(
B
0
â
Ï
±
Ό
â
)
Measurement of CP -violating and mixing-induced observables in Bs0âÏÎł decays
A time-dependent analysis of the
B
0
s
â
Ï
Îł
decay rate is performed to determine the
C
P
-violating observables
S
Ï
Îł
and
C
Ï
Îł
and the mixing-induced observable
A
Î
Ï
Îł
. The measurement is based on a sample of
p
p
collision data recorded with the LHCb detector, corresponding to an integrated luminosity of
3
â
â
fb
â
1
at center-of-mass energies of 7 and 8 TeV. The measured values are
S
Ï
Îł
=
0.43
±
0.30
±
0.11
,
C
Ï
Îł
=
0.11
±
0.29
±
0.11
, and
A
Î
Ï
Îł
=
â
0.67
+
0.37
â
0.41
±
0.17
, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables
S
and
C
in radiative
B
0
s
decays. The results are consistent with the standard model predictions
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