7,442 research outputs found
X-ray transition yields of low-Z kaonic atoms produced in Kapton
The X-ray transition yields of kaonic atoms produced in Kapton polyimide
(C22H10N2O5) were measured for the first time in the SIDDHARTA experiment.
X-ray yields of the kaonic atoms with low atomic numbers (Z = 6, 7, and 8) and
transitions with high principal quantum numbers (n = 5-8) were determined. The
relative yield ratios of the successive transitions and those of
carbon-to-nitrogen (C:N) and carbon-to-oxygen (C:O) were also determined. These
X-ray yields provide important information for understanding the capture ratios
and cascade mechanisms of kaonic atoms produced in a compound material, such as
Kapton.Comment: Accepted in Nucl. Phys. A (2013
Strong interaction studies with kaonic atoms
The strong interaction of antikaons (K-) with nucleons and nuclei in the low
energy regime represents an active research field connected intrinsically with
few-body physics. There are important open questions like the question of
antikaon nuclear bound states - the prototype system being K-pp. A unique and
rather direct experimental access to the antikaon-nucleon scattering lengths is
provided by precision X-ray spectroscopy of transitions in low-lying states of
light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment
at the electron-positron collider DA?NE of LNF-INFN we measured the most
precise values of the strong interaction observables, i.e. the strong
interaction on the 1s ground state of the electromagnetically bound K-p atom
leading to a hadronic shift and a hadronic broadening of the 1s state. The
SIDDHARTA result triggered new theoretical work which achieved major progress
in the understanding of the low-energy strong interaction with strangeness.
Antikaon-nucleon scattering lengths have been calculated constrained by the
SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent
scattering lengths a measurement of the hadronic shift and width of kaonic
deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic
deuterium are in preparation (SIDDHARTA2). Many improvements in the
experimental setup will allow to measure kaonic deuterium which is challenging
due to the anticipated low X-ray yield. Especially important are the data on
the X-ray yields of kaonic deuterium extracted from a exploratory experiment
within SIDDHARTA.Comment: Proc. Few Body 21, 4 pages, 2 figure
Preliminary study of kaonic deuterium X-rays by the SIDDHARTA experiment at DAFNE
The study of the KbarN system at very low energies plays a key role for the
understanding of the strong interaction between hadrons in the strangeness
sector. At the DAFNE electron-positron collider of Laboratori Nazionali di
Frascati we studied kaonic atoms with Z=1 and Z=2, taking advantage of the
low-energy charged kaons from Phi-mesons decaying nearly at rest. The SIDDHARTA
experiment used X-ray spectroscopy of the kaonic atoms to determine the
transition yields and the strong interaction induced shift and width of the
lowest experimentally accessible level (1s for H and D and 2p for He). Shift
and width are connected to the real and imaginary part of the scattering
length. To disentangle the isospin dependent scattering lengths of the
antikaon-nucleon interaction, measurements of Kp and of Kd are needed. We
report here on an exploratory deuterium measurement, from which a limit for the
yield of the K-series transitions was derived: Y(K_tot)<0.0143 and
Y(K_alpha)<0.0039 (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium
experiment is introduced.Comment: Accepted by Nuclear Physics
Unprecedented studies of the low-energy negatively charged kaons interactions in nuclear matter by AMADEUS
The AMADEUS experiment aims to provide unique quality data of hadronic
interactions in light nuclear targets, in order to solve fundamental open
questions in the non-perturbative strangeness QCD sector, like the
controversial nature of the state, the yield of hyperon
formation below threshold, the yield and shape of multi-nucleon
absorption, processes which are intimately connected to the possible existence
of exotic antikaon multi-nucleon clusters. AMADEUS takes advantage of the
DANE collider, which provides a unique source of monochromatic
low-momentum kaons and exploits the KLOE detector as an active target, in order
to obtain excellent acceptance and resolution data for nuclear capture on
H, He, Be and C, both at-rest and in-flight. During the
second half of 2012 a successful data taking was performed with a dedicated
pure carbon target implemented in the central region of KLOE, providing a high
statistic sample of pure at-rest nuclear interactions. For the future
dedicated setups involving cryogenic gaseous targets are under preparation.Comment: 14 pages, 6 figure
-series X-ray yield measurement of kaonic hydrogen atoms in a gaseous target
We measured the -series X-rays of the exotic atom in the
SIDDHARTA experiment with a gaseous hydrogen target of 1.3 g/l, which is about
15 times the of hydrogen gas. At this density, the absolute
yields of kaonic X-rays, when a negatively charged kaon stopped inside the
target, were determined to be 0.012 for and
0.043 for all the -series transitions . These
results, together with the KEK E228 experiment results, confirm for the first
time a target density dependence of the yield predicted by the cascade models,
and provide valuable information to refine the parameters used in the cascade
models for the kaonic atoms.Comment: 9 pages, 5 figures. Submitted to Nuclear Physics A, Special Issue on
Strangeness and Char
Measurement of the strong interaction induced shift and width of the 1s state of kaonic deuterium at J-PARC
The antikaon-nucleon interaction close to threshold provides crucial
information on the interplay between spontaneous and explicit chiral symmetry
breaking in low-energy QCD. In this context the importance of kaonic deuterium
X-ray spectroscopy has been well recognized, but no experimental results have
yet been obtained due to the difficulty of the measurement. We propose to
measure the shift and width of the kaonic deuterium 1s state with an accuracy
of 60 eV and 140 eV respectively at J-PARC. These results together with the
kaonic hydrogen data (KpX at KEK, DEAR and SIDDHARTA at DAFNE) will then permit
the determination of values of both the isospin I=0 and I=1 antikaon-nucleon
scattering lengths and will provide the most stringent constraints on the
antikaon-nucleon interaction, promising a breakthrough. Refined Monte Carlo
studies were performed, including the investigation of background suppression
factors for the described setup. These studies have demonstrated the
feasibility of determining the shift and width of the kaonic deuterium atom 1s
state with the desired accuracy of 60 eV and 140 eV.Comment: 12 pages, 9 figure
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Study of CP violation in Dalitz-plot analyses of B0 --> K+K-KS, B+ --> K+K-K+, and B+ --> KSKSK+
We perform amplitude analyses of the decays , , and , and measure CP-violating
parameters and partial branching fractions. The results are based on a data
sample of approximately decays, collected with the
BABAR detector at the PEP-II asymmetric-energy factory at the SLAC National
Accelerator Laboratory. For , we find a direct CP asymmetry
in of , which differs
from zero by . For , we measure the
CP-violating phase .
For , we measure an overall direct CP asymmetry of
. We also perform an angular-moment analysis of
the three channels, and determine that the state can be described
well by the sum of the resonances , , and
.Comment: 35 pages, 68 postscript figures. v3 - minor modifications to agree
with published versio
Observation and Mass Measurement of the Baryon
We report the observation and measurement of the mass of the bottom, strange
baryon through the decay chain , where
, , and .
Evidence for observation is based on a signal whose probability of arising from
the estimated background is 6.6 x 10^{-15}, or 7.7 Gaussian standard
deviations. The mass is measured to be (stat.) (syst.) MeV/.Comment: Minor text changes for the second version. Accepted by Phys. Rev.
Let
First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0
decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the
neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S
omega. The measurement is performed combining the final data samples collected
at the Y(4S) resonance by the BaBar and Belle experiments at the
asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The
data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar
detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We
measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06
(syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results
correspond to the first observation of CP violation in B0->D(*)CP h0 decays.
The hypothesis of no mixing-induced CP violation is excluded in these decays at
the level of 5.4 standard deviations.Comment: 9 pages, 2 figures, submitted to Physical Review Letter
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