Search for π0 decays to invisible particles Cortina Gil, E.; Minucci, E.; Padolski, S. ...
The journal of high energy physics,
02/2021, Letnik:
2021, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A
bstract
The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 10
9
tagged
π
0
mesons from
K
+
→
π
+
π
0
(
γ
), searching for the decay of the
π
0
to invisible particles. No signal ...is observed in excess of the expected background fluctuations. An upper limit of 4
.
4 × 10
−
9
is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay
K
+
→
π
+
X
, where
X
is a particle escaping detection with mass in the range 0.110–0.155 GeV
/c
2
and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming
X
to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.
We report results from a new measurement of the K
e4
decay K
±
→π
+
π
-
e
±
ν by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 K
e4
decays in both charged ...modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δ
s
-δ
p
) have been measured in ten independent bins of the ππ mass spectrum to investigate their variation. A sizeable acceptance at large ππ mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the ππ scattering lengths a
0
0
and a
0
2
. Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a
0
0
,a
0
2
): a
0
0
=0.233±0.016stat±0.007syst,a
0
2
=-0.0471±0.011stat±0.004syst. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory.
Some optimization of the transition radiation detector Astabatyan, R.A; Lobastov, S.P; Madigojine, D.T ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2001, Letnik:
457, Številka:
1
Journal Article
Recenzirano
Calculation results for the registration of the isolated 10 GeV/
c pions and electrons in the straw TRD detector are presented. Different techniques of signal processing have been used: cluster ...counting (
N method), total energy deposition (
Q method) and two-dimensional spectra (
Q,
N method). Calculations were carried out for different modifications of the detector module.
Correlations of pairs of {lambda} hyperons, neutral kaons, and charged pions having a low relative momentum are analyzed on the basis of data obtained at the EXCHARM facility in neutron-carbon ...interactions at an average neutron energy of 51 GeV. Preliminary results of this analysis are presented.
The inclusive production cross-sections of \(\bar\Lambda^0\), \(\bar\Xi^+\), and \(\bar\Sigma(1385)^\pm\) in neutron-carbon interactions at \(\sim 51\) GeV mean energy of neutrons have been measured. ...The parameters n and b of differential cross-section parametrisation \((1-\vert x_F\vert)^n\cdot\exp (-bp_t^2)\), where xF is the Feynman variable, pt is the transverse momentum, have been obtained. The kinematic region of validity of the parametrisation has been defined. Results are compared with published experimental data.
The NA62 experiment at the CERN SPS reports the first search for K+→π+νν¯ using the decay-in-flight technique, based on a sample of 1.21×1011K+ decays collected in 2016. The single event sensitivity ...is 3.15×10−10, corresponding to 0.267 Standard Model events. One signal candidate is observed while the expected background is 0.152 events. This leads to an upper limit of 14×10−10 on the K+→π+νν¯ branching ratio at 95% CL.
Abstract
We report the results of a search for dark photon in-flight decays to
μ
+
μ
−
pairs at NA62. Dark photons could be produced by dumping protons onto a copper-iron absorber, reach the NA62 ...decay volume more than 80 m downstream of the dump and decay therein. The measurement is based on data collected in 2021 which correspond to 1.4 × 10
17
dumped protons.
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