M. Bazzi

A New Measurement of Kaonic Hydrogen X-rays

The KN system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the K-series x rays of kaonic hydrogen atoms at the DANE electron-positron collider of Laboratori Nazionali di Frascati, and have de- termined the most precise values of the strong-interaction energy-level shift and width of the 1s atomic state. As x-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be ǫ1s = 283 ± 36(stat) ± 6(syst) eV and 1s = 541± 89(stat) ± 22(syst) eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy KN interaction.

Kaonic hydrogen X-ray measurement in SIDDHARTA

Abstract Kaonic hydrogen atoms provide a unique laboratory to probe the kaon–nucleon strong interaction at the energy threshold, allowing an investigation of the interplay between spontaneous and explicit chiral symmetry breaking in low-energy QCD. The SIDDHARTA Collaboration has measured the K -series X rays of kaonic hydrogen atoms at the DAΦNE electron–positron collider of Laboratori Nazionali di Frascati, and has determined the most precise values of the strong-interaction induced shift and width of the 1 s atomic energy level. This result provides vital constraints on the theoretical description of the low-energy K ¯ N interaction.

First measurement of kaonic helium-3 X-rays

The first observation of the kaonic 3He 3d→2p transition was made, using slow K− mesons stopped in a gaseous 3He target. The kaonic atom X-rays were detected with large-area silicon drift detectors using the timing information of the K+K− pairs of ϕ-meson decays produced by the DAΦNE e+e− collider. The strong interaction shift of the kaonic 3He 2p state was determined to be −2±2(stat)±4(syst) eV.Scattering of fermion off dilaton black hole has been extensively studied over the years [1–3, 5–11] and it has provided much insight into its connection to the Hawking radiation. Even after the intensive investigations it remains as a subject of several interests because of the subtleties involved in it in connection with information loss scenario during the formation and subsequent evaporation of black hole. It is worth mentioning at this stage that a controversy in this context was generated from the Hawking’s suggestion [1] three decades ago. However his recent suggestion on this issue [4] has brought back a pretty pleasant scenario. It may even be thought that the controversy has come to an end. General description of such scattering problem is extremely difficult. Despite that, there have been attempts in studying such problem in its full complexity through the s-matrix description of such event [2]. Comparatively less complicated model therefore entered into the picture and showed its prominent role in this issue [5–9]. The toy model due to Alford and Strominger [5] provides an interesting description of the s-wave scattering of fermion off dilaton black hole with a trustworthy results concerning information loss. It helps to avoid some of the technical obstacle posed by quantum gravity in (3 + 1). Even in the presence of gravitational anomaly a systematic description of this scattering of fermion off dilaton would have been possible through this model [10, 11]. The provision of taking the effect of one loop correction [12, 13] into consideration is also an exiting aspect of this model. That indeed shows a way to investigate the effect of anomaly [10, 11] on this scattering phenomena. Notably, this model arose in two dimensional non-critical string theory and its black hole solution was discovered in [14]. Few years back Mitra studied this scattering problem replacing Dirac fermion by chiral fermion and found an uncomfortable scenario [10]. He observed that information failed to be preserved. With the use of anomaly we have shown that that disaster can be avoided [11]. Anomaly played there a very surprising as well as interesting role. Seeing the interesting role of anomaly on the s-wave scattering of chiral fermion [10, 11] we are intended here to investigate the role of one loop correction on the s-wave scattering of Dirac fermion using the said toy model due to Alford and Strominger [5]. Needless to mention that the counter term appeared here due to one loop correction looks similar to the term used in [11].

Preliminary study of kaonic deuterium X-rays by the SIDDHARTA experiment at DAΦNE

The study of the K¯N system at very low energies plays a key role for the understanding of the strong interaction between hadrons in the strangeness sector. At the DAΦNE 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 Φ-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 K−p and of K−d 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(Ktot)<0.0143 and Y(Kα)<0.0039 (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium experiment is introduced.

Measurements of the strong-interaction widths of the kaonic 3He and 4He 2p levels

The kaonic 3He and 4He X-rays emitted in the 3d→2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Γ2p(He3)=6±6(stat.)±7 (syst.) eV, and Γ2p(He4)=14±8 (stat.)±5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55±34 eV determined by the experiments performed in the 70ʼs and 80ʼs, while the width of kaonic 3He was determined for the first time.

Test of the Pauli Exclusion Principle in the VIP-2 underground experiment

The validity of the Pauli exclusion principle—a building block of Quantum Mechanics—is tested for electrons. The VIP (violation of Pauli exclusion principle) and its follow-up VIP-2 experiments at the Laboratori Nazionali del Gran Sasso search for X-rays from copper atomic transitions that are prohibited by the Pauli exclusion principle. The candidate events—if they exist—originate from the transition of a 2 p orbit electron to the ground state which is already occupied by two electrons. The present limit on the probability for Pauli exclusion principle violation for electrons set by the VIP experiment is 4.7 × 10 − 29 . We report a first result from the VIP-2 experiment improving on the VIP limit, which solidifies the final goal of achieving a two orders of magnitude gain in the long run.

Spontaneously Emitted X-rays: An Experimental Signature of the Dynamical Reduction Models

We present the idea of searching for X-rays as a signature of the mechanism inducing the spontaneous collapse of the wave function. Such a signal is predicted by the continuous spontaneous localization theories, which are solving the “measurement problem” by modifying the Schrödinger equation. We will show some encouraging preliminary results and discuss future plans and strategy.

Characterization of a scintillating fibers read by MPPC detectors trigger prototype for the AMADEUS experiment

Multi-Pixel Photon Counters (MPPC) consist of hundreds of micro silicon Avalanche PhotoDiodes (APD) working in Geiger mode. The high gain and the low noise, typical of these devices, together with their good performance in magnetic field, make them ideal readout detectors for scintillating fibers as trigger detectors in particle and nuclear physics experiments like AMADEUS, where such detectors are planned to be used to trigger on charged kaon pairs. In order to investigate the detection efficiency of such a system, a prototype setup consisting of 32, 1 mm diameter scintillating fibers, arranged in two double layers of 16 fibers each, and read out by 64 MPPCs with an ad-hoc built readout electronics, was tested at the piM-1 line of the Paul Scherrer Institute (PSI) in Villigen, Switzerland. The detection efficiency and the trigger capability were measured on a beam containing protons, electrons, muons and pions with a momentum of 440 MeV/c. The measured average efficiency for protons for a double layer of scintillating fibers (96.9 +/-1.2%) represents a guarantee of the good performance of this system as a trigger for the AMADEUS experiment.

X-ray transition yields of low-Z kaonic atoms produced in Kapton

Abstract 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 yields of the successive transitions in the same atoms and the yield ratios of carbon-to-nitrogen (C:N) and carbon-to-oxygen (C:O) for the same transitions 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.

Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction

In the exotic atoms where one atomic 1s electron is replaced by a K − , the strong interaction between the K − and the nucleus introduces an energy shift and broadening of the low-lying kaonic atomic levels which are determined by only the electromagnetic interaction. By performing X-ray spectroscopy for Z = 1,2 kaonic atoms, the SIDDHARTA experiment determined with high precision the shift and width for the 1s state of K − p and the 2p state of kaonic helium-3 and kaonic helium-4. These results provided unique information of the kaon-nucleus interaction in the low energy limit.