38 research outputs found
Hunting the "impossible atoms" Pauli exclusion principle violation and spontaneous collapse of the wave function at test
The Pauli exclusion principle (PEP) and, more generally, the spin-statistics connection, are at the very basis of our understanding of matter, life and Universe. The PEP spurs, presently, a lively debate on its possible limits, deeply rooted in the very foundations of Quantum Mechanics. It is, therefore, extremely important to test the limits of its validity. The Violation of the PEP (VIP) experiment established the best limit on the probability that PEP is violated by electrons, using the method of searching for PEP forbidden atomic transitions in copper. We describe the experimental method, the obtained results, and plans to go beyond the actual limit by upgrading the experimental apparatus. We discuss the possibility of using a similar experimental technique to search for X-rays as a signature of the spontaneous collapse of the wave function predicted by continuous spontaneous localization (CSL) theories
Recent AMADEUS studies of low-energy - nucleus/nuclei interactions
We briefly report the recent results obtained by the AMADEUS collaboration on experimental studies of the K- low-energy interactions with light nuclei and outline the future perspectives
The X-ray machine for the examination of quantum mechanics
By performing X-rays measurements in the underground laboratory of Gran Sasso, LNGS-INFN, we test a basic principle of quantum mechanics: the Pauli exclusion principle (PEP). In the future, we aim to use a similar experimental technique to search for X-rays as a signature of the spontaneous collapse of the wave function predicted by continuous spontaneous localization theories. We present the achieved results of the VIP experiment and the future plans to gain two orders of magnitude in testing PEP with the recently VIP2 setup installed at Gran Sasso
Search for heavy neutral lepton production in decays
A search for heavy neutral lepton production in decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the to level are established on the elements of the extended neutrino mixing matrix () for heavy neutral lepton mass in the range . This improves on the results from previous production searches in decays, setting more stringent limits and extending the mass range.A search for heavy neutral lepton production in K+ decays using a data sample collected with a minimum bias trigger by the NA62 experiment at CERN in 2015 is reported. Upper limits at the 10−7 to 10−6 level are established on the elements of the extended neutrino mixing matrix |Ue4|2 and |Uμ4|2 for heavy neutral lepton mass in the ranges 170–448 MeV/ c2 and 250–373 MeV/ c2 , respectively. This improves on the previous limits from HNL production searches over the whole mass range considered for |Ue4|2 , and above 300 MeV/ c2 for |Uμ4|2
First search for using the decay-in-flight technique
International audienceThe 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 1.21×1011 K+ 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
Search for decays to a muon and invisible particles
The NA62 experiment at CERN reports searches for and decays, where and are massive invisible particles, using the 2016-2018 data set. The particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of of the neutrino mixing parameter for masses in the range 200-384 MeV/ and lifetime exceeding 50 ns. The particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for masses in the range 10-370 MeV/ are reported for the first time, ranging from to . An improved upper limit of is established at 90% CL on the branching fraction.The NA62 experiment at CERN reports searches for K+→μ+N and K+→μ+νX decays, where N and X are massive invisible particles, using the 2016–2018 data set. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of O(10−8) of the neutrino mixing parameter |Uμ4|2 for N masses in the range 200–384 MeV/ c2 and lifetime exceeding 50 ns. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for X masses in the range 10–370 MeV/ c2 are reported for the first time, ranging from O(10−5) to O(10−7) . An improved upper limit of 1.0×10−6 is established at 90% CL on the K+→μ+ννν¯ branching fraction.The NA62 experiment at CERN reports searches for and decays, where and are massive invisible particles, using the 2016-2018 data set. The particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of of the neutrino mixing parameter for masses in the range 200-384 MeV/ and lifetime exceeding 50 ns. The particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for masses in the range 10-370 MeV/ are reported for the first time, ranging from to . An improved upper limit of is established at 90% CL on the branching fraction
Measurement of the very rare decay
The NA62 experiment reports the branching ratio measurement BR at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016-2018. This provides evidence for the very rare decay, observed with a significance of 3.4. The experiment achieves a single event sensitivity of , corresponding to 10.0 events assuming the Standard Model branching ratio of . This measurement is also used to set limits on BR(), where is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample
Search for decays to invisible particles
The NA62 experiment at the CERN SPS reports a study of a sample of tagged mesons from , searching for the decay of the to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 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 where is a particle escaping detection with mass in the range GeV/ and rest lifetime greater than 100 ps. Model- dependent upper limits are obtained assuming to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs.The NA62 experiment at the CERN SPS reports a study of a sample of tagged mesons from , searching for the decay of the to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 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 , where is a particle escaping detection with mass in the range 0.110-0.155 GeV and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson