CERN Accelerating science

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1.
First measurement of a long-lived π+π atom lifetime / DIRAC Collaboration
The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogen-like π+π atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96~mm and got broken up in the 2.1~\textmu{}m thick platinum foil. [...]
arXiv:1811.08659; CERN-EP-2018-281; DIRAC-PUB-2019-01.- Geneva : CERN, 2019-03-01 - 7 p. - Published in : Phys. Rev. Lett. 122 (2019) 082003 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: 1811.08659 - PDF; CERN-EP-2018-281 - PDF;
2.
Detection of π+π atoms with the DIRAC spectrometer at CERN / DIRAC Collaboration
The goal of the DIRAC experiment at CERN is to measure with high precision the lifetime of the π+π atom (A2π), which is of order 3×1015 s, and thus to determine the s-wave ππ-scattering lengths difference |a0a2|. A2π atoms are detected through the characteristic features of π+π pairs from the atom break-up (ionization) in the target. [...]
hep-ex/0409053; DIRAC-PUB-2004-03.- 2004 - 19 p. - Published in : J. Phys. G 30 (2004) 1929-1946 Access to fulltext document: PDF; Fulltext: PDF; External link: hep-ex/0409053 PDF
3.
Observation of πK+ and π+K atoms / DIRAC Collaboration
The observation of hydrogen-like πK atoms, consisting of πK+ or π+K mesons, is presented. The atoms have been produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. [...]
arXiv:1605.06103; CERN-EP-2016-128; DIRAC-PUB-2016-02.- Geneva : CERN, 2016-09-08 - 6 p. - Published in : Phys. Rev. Lett. 117 (2016) 112001 Draft (restricted): PDF; Fulltext: arXiv:1605.06103 - PDF; 10.1103_PhysRevLett.117.112001 - PDF; PhysRevLett.117.112001 - PDF; Preprint: PDF; External link: Fulltext
4.
The π+π Coulomb interaction study and its use in the data processing / Adeva, B. (Santiago de Compostela U.) ; Afanasyev, L. (Dubna, JINR) ; Anania, A. (INFN, Messina) ; Aogaki, S. (Bucharest, IFIN-HH) ; Benelli, A. (Prague, Tech. U.) ; Brekhovskikh, V. (Serpukhov, IHEP) ; Cechak, T. (Prague, Tech. U.) ; Chiba, M. (Tokyo Metropolitan U.) ; Chliapnikov, P. (Serpukhov, IHEP) ; Drijard, D. (Prague, Tech. U. ; CERN) et al.
In this work the Coulomb effects (Coulomb correlations) were studied using experimental π+π pair distributions in Q, the relative momentum in the pair center of mass system (c.m.s), and its projections QL (longitudinal component) and Qt (transverse component) relative to the pair direction in the laboratory system (l.s.). The major part of the pion pairs is produced by decay of ρ,ω and Δ and other short-lived sources (Coulomb pairs). [...]
arXiv:2409.12696; CERN-EP-2023-276.- Geneva : CERN, 2024-11-01 - 11 p. - Published in : Phys. Rev. D 110 (2024) 092005 Draft (restricted): PDF; Fulltext: DIRAC-Coulomb-correct - PDF; 2409.12696 - PDF;
5.
Investigation of K+K pairs in the effective mass region near 2mK / DIRAC Collaboration
The DIRAC experiment at CERN investigated in the reaction p(24 GeV/c)+Ni the particle pairs K+K,π+π and pp¯ with relative momentum Q in the pair system less than 100 MeV/c. Because of background influence studies, DIRAC explored three subsamples of K+K pairs, obtained by subtracting -- using time-of-flight (TOF) technique -- background from initial Q distributions with K+K sample fractions more than 70%, 50% and 30%. [...]
arXiv:2204.01857; CERN-EP-2022-058.- 2022-08-01 - 18 p. - Published in : Phys. Rev. D 106 (2022) 032006 Fulltext: PhysRevD.106.032006 - PDF; 2204.01857 - PDF;
6.
Determination of ππ scattering lengths from measurement of π+π atom lifetime / PS212 collaboration
The DIRAC experiment at CERN has achieved a sizeable production of π+π atoms and has significantly improved the precision on its lifetime determination. From a sample of 21227 atomic pairs, a 4% measurement of the S-wave ππ scattering length difference |a0a2|=(.0.25330.0078+0.0080|stat.0.0073+0.0078|syst)Mπ+1 has been attained, providing an important test of Chiral Perturbation Theory..
arXiv:1109.0569; CERN-PH-EP-2011-028; FERMILAB-PUB-10-713-E; DIRAC-PUB-2011-01.- Geneva : CERN, 2011 - 6 p. - Published in : Phys. Lett. B 704 (2011) 24-29 Draft (restricted): PDF; Fulltext: PDF; Preprint: PDF; External link: Preprint
7.
First observation of long-lived π+π atoms / DIRAC Collaboration
After observing and investigating the double-exotic π+π atom with the ground state lifetime τ of about 3×1015~s, the upgraded DIRAC experiment at the CERN PS accelerator observes for the first time long-lived states of the same atom with lifetimes of about 1011~s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived π+π atoms amounts to 436±61, corresponding to a signal-to-error ratio of better than 7 standard deviations. [...]
arXiv:1508.04712; CERN-PH-EP-2015-175; DIRAC-PUB-2015-02; CERN-PH-EP-2015-175.- Geneva : CERN, 2015-09-26 - 13 p. - Published in : Phys. Lett. B 751 (2015) 12-18 Article from SCOAP3: plb-751-12 - PDF; scoap3-fulltext - PDF; Fulltext: PDF; External link: Preprint
8.
Measurement of the πK atom lifetime and the πK scattering length / DIRAC Collaboration
After having announced the statistically significant observation (5.6~σ) of the new exotic πK atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full πK data sample: τ=(5.52.8+5.0)1015s. By means of a precise relation (<1%) between atom lifetime and scattering length, the following value for the S-wave isospin-odd πK scattering length a0 = 13(a1/2a3/2) has been derived: |a0|=(0.0720.020+0.031)Mπ1..
arXiv:1707.02184; CERN-EP-2017-137; DIRAC-PUB-2017-01.- Geneva : CERN, 2017-09-19 - 18 p. - Published in : Phys. Rev. D 96 (2017) 052002 Draft (restricted): PDF; Fulltext: CERN-EP-2017-137 - PDF; arXiv:1707.02184 - PDF; Fulltext from publisher: PDF;
9.
First observation of πK atom and its lifetime measurement / Adeva, B (Santiago de Compostela U.) ; Afanasiev, L G (Dubna, JINR) ; Berka, Z (Prague, Tech. U.) ; Brekhovskikh, V (Serpukhov, IHEP) ; Caragheorgheopol, G (Bucharest, IFIN-HH) ; Cechák, T (Prague, Tech. U.) ; Chiba, M (Tokyo Metropolitan U.) ; Costantini, S (Basel U.) ; Constantinescu, S (Bucharest, IFIN-HH) ; Détraz, C (CERN) et al.
CERN-SPSC-2000-032 ; SPSC-P-284-ADD-2 ; DIRAC-NOTE-2000-09 ; DIRAC-DOC-2000-01.
- 2000. - 75 p.
Fulltext - Fulltext
10.
First πK atom lifetime and πK scattering length measurements / DIRAC Collaboration
The results of a search for hydrogen-like atoms consisting of πK± mesons are presented. Evidence for πK atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic πK pairs from their breakup in the same target (178±49) and from Coulomb final state interaction (653±42). [...]
arXiv:1403.0845; CERN-PH-EP-2014-030; DIRAC-PUB-2014-01; CERN-PH-EP-2014-030.- Geneva : CERN, 2014-07-30 - 7 p. - Published in : Phys. Lett. B 735 (2014) 288-294 Article from SCOAP3: PDF; Draft (restricted): PDF; Fulltext: PDF; Preprint: PDF;

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