0000000000256264
AUTHOR
Shama Ahmad
The ASTERIX spectrometer at LEAR
The ASTERIX spectrometer has been used to study the formation and the ground state of the pp atom and exclusive final states of pp annihilation at rest in a H2 gas target at NTP, using antiprotons from the Low Energy Antiproton Ring (LEAR) at CERN. The article describes the mechanical construction of the apparatus, the trigger logic, the chamber readout, and the data acquisition system. The detector calibration and the offline processing of the 55 million reconstructed events are illustrated. An overview is given about the new physics results obtained by the experiment.
Jet-associated deuteron production in pp collisions at s=13 TeV
Author(s): Acharya, S; Adamova, D; Adler, A; Adolfsson, J; Aglieri Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, SU; Akbar, Z; Akindinov, A; Al-Turany, M; Albuquerque, DSD; Aleksandrov, D; Alessandro, B; Alfanda, HM; Alfaro Molina, R; Ali, B; Ali, Y; Alici, A; Alizadehvandchali, N; Alkin, A; Alme, J; Alt, T; Altenkamper, L; Altsybeev, I; Anaam, MN; Andrei, C; Andreou, D; Andronic, A; Angeletti, M; Anguelov, V; Anticic, T; Antinori, F; Antonioli, P; Apadula, N; Aphecetche, L; Appelshauser, H; Arcelli, S; Arnaldi, R; Arratia, M; Arsene, IC; Arslandok, M; Augustinus, A; Averbeck, R; Aziz, S; Azmi, MD; Badala, A; Baek, YW; Bai, X; Bailhache, R; Bala, R; Balbino, A; Baldisseri, …
Antiproton-proton annihilation at rest intoπ + π − η ′ andπ + π − η from atomicS andP states
We have measured the branching ratios for\(\bar pp\) annihilation at rest intoπ+π−η andπ+π−η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for\(\bar pp\) annihilations into four charged pions of (49±4)% and the branching ratio intoπ+π−π+π−π0 of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for\(\bar pp \to \pi ^ + \pi ^ - \eta \) andπ+π−η′ in comparison toS-state annihilation. $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta ) = (13.7 \pm 1.46) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta …
Observation and analysis ofE mesons in $$\bar p$$ p annihilation at rest in H2 gas
Antiproton-proton annihilation at rest in a gaseous H2 target at NTP into the final state π+ π−K± π∓ (K0) with an undetectedK0 or\(\bar K^0 \) has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K0)missK± π∓ with massME=1413±8 MeV/c2 and widthГE=62 ± 16MeV/c2 and find evidence for the production of thef1(1285). The absolute branching ratio of\(\bar p\)p → π+ π−E0,E0 →K0LK±π∓ at (61±6)%P wave annihilation is (3.0±0.9)·10−4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJpc=0−+ and not I++.