We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) ...mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively.
The concept of Virtual Monte Carlo (VMC) allows to use different Monte Carlo programs to simulate particle physics detectors without changing the geometry definition and the detector response ...simulation. In this context, to study the reconstruction capabilities of a detector, the availability of a tool to extrapolate the track parameters and their associated errors due to magnetic field, straggling in energy loss and Coulomb multiple scattering plays a central role: GEANE is an old program written in Fortran 15 years ago that performs this task through dense materials and that is still succesfully used by many modern experiments in its native form. Among its features there is the capability to read directly the geometry and the magnetic field map from the simulation and to use different track representations. In this work we have rediscovered GEANE in the context of the Virtual Monte Carlo: we will show how GEANE has been integrated in the FairROOT framework, firmly based on the VMC, by keeping the old features in the new ROOT geometry modeler. Moreover new features have been added to GEANE that allow one to use it also for low density materials, i.e. for gaseous detectors, and preliminary results will be shown and discussed. The tool is now used by the PANDA and CBM collaborations at GSI as the first step for the global reconstruction algorithms, based on a Kalman filter which is currently under development.
Distributions of absorbed dose and DNA clustered damage yields in various organs and tissues following the October 1989 solar particle event (SPE) were calculated by coupling the FLUKA Monte Carlo ...transport code with two anthropomorphic phantoms (a mathematical model and a voxel model), with the main aim of quantifying the role of the shielding features in modulating organ doses. The phantoms, which were assumed to be in deep space, were inserted into a shielding box of variable thickness and material and were irradiated with the proton spectra of the October 1989 event. Average numbers of DNA lesions per cell in different organs were calculated by adopting a technique already tested in previous works, consisting of integrating into “condensed-history” Monte Carlo transport codes – such as FLUKA – yields of radiobiological damage, either calculated with “event-by-event” track structure simulations, or taken from experimental works available in the literature. More specifically, the yields of “Complex Lesions” (or “CL”, defined and calculated as a clustered DNA damage in a previous work) per unit dose and DNA mass (CL Gy
−1 Da
−1) due to the various beam components, including those derived from nuclear interactions with the shielding and the human body, were integrated in FLUKA. This provided spatial distributions of CL/cell yields in different organs, as well as distributions of absorbed doses. The contributions of primary protons and secondary hadrons were calculated separately, and the simulations were repeated for values of Al shielding thickness ranging between 1 and 20 g/cm
2. Slight differences were found between the two phantom types. Skin and eye lenses were found to receive larger doses with respect to internal organs; however, shielding was more effective for skin and lenses. Secondary particles arising from nuclear interactions were found to have a minor role, although their relative contribution was found to be larger for the Complex Lesions than for the absorbed dose, due to their higher LET and thus higher biological effectiveness.
With experimental data of
annihilation at rest on nuclei of
4
He, collected by the Obelix spectrometer (LEAR, CERN), we have studied a number of reactions with 4 and 5 charged particles in the final ...state, distinguishing the annihilations on more than one nucleon, and with strangeness production. The main results of our observations are: (a) a higher (up to 20 times) strangeness production in
4
He than in H; (b) the evidence of a possible signature of a
(
) bound state; (c) a measurement of a double strangeness production (2
K
+
) and a hint for some production yields of double-strange bound systems like 2
K
−
2
n
; (d) a signal compatible with the baryonic
resonance, interpreted as a pentaquark system.
We developed an electronic system which, used with drift chambers, allows to perform a precise charge division measurement of the longitudinal coordinate, even if the sense wire is held at high ...voltage and a decoupling capacitor is needed. The idea is to create a temporal gate at the arrival of the signal and transmit to the ADC only this part of the signal. The gate remains open for a short period
(120
ns)
, corresponding to the duration of the anode pulse and delivers, at its output, a pulse of amplitude linearly dependent from the input value. In this way the systematic error is better than 1% of the wire length. It introduces a considerable improvement in comparison with previously used software corrections, mainly from the linearity and simplicity point of view.
This paper provides a summary of the first results obtained by the FINUDA Collaboration in the field of hypernuclear physics. They range from the spectroscopic study of several A-hypernuclei to the ...observation of some non-mesonic decay modes. Hints on rare hypernuclear two-body decays, on neutron-rich hypernuclei and on deeply-bound kaonic nuclei are also reported.
In spring 2003 the FINUDA detector was installed at the
ϕ factory DAΦNE in the Laboratori Nazionali di Frascati of INFN (Italy). In October 2003 the commissioning of the apparatus was accomplished ...and the first data taking started with a set of nuclear targets
6Li,
7Li,
natC,
27Al,
51V. The data collection will continue until a total integrated luminosity of
250
pb
−1
is recorded. Light and medium
A hypernuclei will be abundantly produced by the strangeness exchange reaction induced by the stopped
K
−
coming from the decay of
ϕ
(
1020
)
mesons.
The aim of the experiment is to simultaneously measure the excitation energy spectra of the produced hypernuclei, with a resolution better than 1 MeV, the lifetime of the
Λ embedded in the different hypernuclei and the partial widths
Γ
π
,
Γ
n
p
and
Γ
n
n
for mesonic and non-mesonic hypernuclear decays. Information on neutron-rich hypernuclei and rare hypernuclear two-body decays might be available too, with the statistics that will be collected at the end of the run.
In the present paper, first results concerning in-beam detector calibration, spectrometer performances and very preliminary hypernuclear formation and decay spectra will be presented.
The dependence of the
K
+
and
K
−
production on the number of nucleons involved in the annihilation process is investigated experimentally in the
p
¯
annihilation at rest on hydrogen, deuterium,
3He ...and
4He gas targets. Annihilations with any number of prongs (charged pions and kaons, protons and deuterons) are analyzed. Events with and without production of neutral mesons and with and without emission of fast neutrons (that is neutrons involved in the annihilation process) are recognized. The results are consistent with our previous ones on a more restricted sample of annihilation reactions and put in evidence that the strangeness production is lower or higher depending on the reaction channel. As a general trend, the strangeness production is higher in events without neutral mesons and still higher in events with the involvement of a higher number of nucleons. Both
K
+
and
K
−
productions increase with the number of involved nucleons, but
K
+
much more. The maximum
K
+
production is observed in the reaction
K
+
2
π
+
2
π
−
3
n
on
4He (with the involvement of 3–4 nucleons); compared with the production on hydrogen in the reaction
K
+
π
+
2
π
−
, the production on
4He is higher by a factor of
31.7
±
5.5
. In the light of some theoretical speculations, this enhancement factor is too high to be explainable in terms of hadronic interactions and could be interpreted as a signature of quark deconfinement and of formation of a quark–gluon plasma.
The FINUDA experiment performed a systematic study of the charged mesonic weak decay channel of p-shell Λ-hypernuclei. Negatively charged pion spectra from mesonic decay were measured with magnetic ...analysis for the first time for 7ΛLi, 9ΛBe, 11ΛB and 15ΛN. The shape of the π− spectra was interpreted through a comparison with pion distorted wave calculations that take into account the structure of both hypernucleus and daughter nucleus. Branching ratios Γπ−/Γtot were derived from the measured spectra and converted to π− decay rates Γπ− by means of known or extrapolated total decay widths Γtot of p-shell Λ-hypernuclei. Based on these measurements, the spin-parity assignment 1/2+ for 7ΛLi and 5/2+ for 11ΛB ground-state are confirmed and a spin-parity 3/2+ for 15ΛN ground-state is assigned for the first time.
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