45 research outputs found
First Observation and Measurement of the Decay K+- -> pi+- e+ e- gamma
Using the full data set of the NA48/2 experiment, the decay K+- -> pi+- e+ e-
gamma is observed for the first time, selecting 120 candidates with 7.3 +- 1.7
estimated background events. With K+- -> pi+- pi0D as normalisation channel,
the branching ratio is determined in a model-independent way to be Br(K+- ->
pi+- e+ e- gamma, m_eegamma > 260 MeV/c^2) = (1.19 +- 0.12_stat +- 0.04_syst) x
10^-8. This measured value and the spectrum of the e+ e- gamma invariant mass
allow a comparison with predictions of Chiral Perturbation Theory.Comment: 13 pages, 3 figures. Accepted for publication in Phys.Lett.
Empirical parameterization of the K+- -> pi+- pi0 pi0 decay Dalitz plot
As first observed by the NA48/2 experiment at the CERN SPS, the \p0p0
invariant mass (M00) distribution from \kcnn decay shows a cusp-like anomaly
at M00=2m+, where m+ is the charged pion mass. An analysis to extract the pi pi
scattering lengths in the isospin I=0 and I=2 states, a0 and a2, respectively,
has been recently reported. In the present work the Dalitz plot of this decay
is fitted to a new empirical parameterization suitable for practical purposes,
such as Monte Carlo simulations of K+- -> pi+- pi0 pi0 decays.Comment: 9 pages, 3 figures
Search for direct CP-violation in K+- --> pi+-pi0pi0 decays
A search for direct CP-violation in K+- --> pi+-pi0pi0 decays based on 47.14
million events has been performed by the NA48/2 experiment at the CERN SPS. The
asymmetry in the Dalitz plot linear slopes A_g=(g^+ - g^-)/(g^+ + g^-) is
measured to be A_g=(1.8 +- 2.6).10^{-4}. The design of the experiment and the
method of analysis provide good control of instrumental charge asymmetries in
this measurement. The precision of the result is limited by statistics and is
almost one order of magnitude better than that of previous measurements by
other experiments.Comment: 14 page
Modeling, optimization, and comparable efficacy of T cell and hematopoietic stem cell gene editing for treating hyper-IgM syndrome
Precise correction of the CD40LG gene in T cells and hematopoietic stem/progenitor cells (HSPC) holds promise for treating X-linked hyper-IgM Syndrome (HIGM1), but its actual therapeutic potential remains elusive. Here, we developed a one-size-fits-all editing strategy for effective T-cell correction, selection, and depletion and investigated the therapeutic potential of T-cell and HSPC therapies in the HIGM1 mouse model. Edited patients' derived CD4 T cells restored physiologically regulated CD40L expression and contact-dependent B-cell helper function. Adoptive transfer of wild-type T cells into conditioned HIGM1 mice rescued antigen-specific IgG responses and protected mice from a disease-relevant pathogen. We then obtained similar to 25% CD40LG editing in long-term repopulating human HSPC. Transplanting such proportion of wild-type HSPC in HIGM1 mice rescued immune functions similarly to T-cell therapy. Overall, our findings suggest that autologous edited T cells can provide immediate and substantial benefits to HIGM1 patients and position T-cell ahead of HSPC gene therapy because of easier translation, lower safety concerns and potentially comparable clinical benefits.Transplantation and immunomodulatio
New measurement of the charged kaon semileptonic (Ke4) decay Branching Ratio and Hadronic Form Factors
A sample of more than one million Ke4 decay candidates with less than one
percent background contamination has been collected by the NA48/2 experiment at
the CERN SPS in 2003-2004, allowing a detailed study of the decay properties.
The branching ratio, inclusive of radiative Ke4gamma decays, is measured to be
BR(Ke4) = (4.257 +/- 0.016_exp +/- 0.031_ext) x 10-5 with a total relative
error of 0.8%. This measurement complements the study of S- and P-wave hadronic
form factors by assigning absolute values to the relative hadronic form factors
obtained earlier in a simultaneous analysis of the pion-pion scattering lengths
conducted on the same data sample. The overall form factor normalization f_s =
5.705 +/- 0.017_exp +/- 0.031_ext is obtained with a total relative precision
of 0.6%.Comment: 21 pages, 5 figures, 5 tables, submitted to Phys. Lett.
Observation of a cusp-like structure in the pizero-pizero invariant mass distribution from K+- ==> pi+- pizero pizero decay and determination of the pi-pi scattering lengths
We report the results from a study of ~23 Million K+- ==> pi+- pizero pizero
decays recorded by the NA48/2 experiment at the CERN SPS, showing an anomaly in
the pizero pizero invariant mass distribution in the region around 2m+, where
m+ is the charged pion mass. This anomaly, never observed in previous
experiments, can be interpreted as an effect due mainly to the final state
charge exchange scattering process pi+ pi- ==> pizero pizero in K+- ==> pi+-
pi+ pi- decay. It provides a precise determination of a0 - a2, the difference
between the pi-pi scattering lengths in the isospin I=0 and I=2 states.Comment: 16 pages, 7 figures Accepted for publication in Physics Letters
Measurement of the Dalitz plot slope parameters of the decay
The distribution of the decays in the Dalitz plot
has been measured by the NA48/2 experiment at the CERN SPS with a sample of
fully reconstructed events. With the standard Particle Data
Group parameterization the following values of the slope parameters were
obtained: , ,
. The quality and statistical accuracy of the data have
allowed an improvement in precision by more than an order of magnitude, and are
such as to warrant a more elaborate theoretical treatment, including pion-pion
rescattering, which is in preparation.Comment: 14 pages, 5 figures. Version submitted to Phys. Lett. B. Slightly
improved analysis and bibliography
First observation and study of the K± → π±π0e+e− decay
The NA48/2 experiment at CERN reports the first observation of the K±→π±π0e+e− decay from an exposure of 1.7×1011 charged kaon decays recorded in 2003-2004. A sample of 4919 candidates with 4.9% background contamination allows the determination of the branching ratio in the full kinematic region, BR(K±→π±π0e+e−)=(4.24±0.14)×10−6. The study of the kinematic space shows evidence for a structure dependent contribution in agreement with predictions based on chiral perturbation theory. Several P- and CP-violating asymmetries are also evaluated
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions