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DIRAC Papers

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2021-06-19
06:25
The estimation of production rates of ${\pi }^{+}{K}^{-}$, ${\pi }^{-}{K}^{+}$ and ${\pi }^{+}{\pi }^{-}$ atoms in proton–nucleus interactions at 450 GeV c(–)(1) / Gorchakov, O E (Dubna, JINR) ; Nemenov, L L (Dubna, JINR)
Short-lived ($\tau \sim 3\times {10}^{-15}\,s$) ${\pi }^{+}{K}^{-}$, ${K}^{+}{\pi }^{-}$ and ${\pi }^{+}{\pi }^{-}$ atoms as well as long-lived ($\tau \geqslant 1\times {10}^{-11}$ s) ${\pi }^{+}{\pi }^{-}$ atoms produced in proton–nucleus interactions at 24 GeV c(–)(1) are observed and studied in the DIRAC experiment at the CERN Proton Synchroton. The purpose of this paper is to show that the yields of the short-lived ${\pi }^{+}{K}^{-}$, ${K}^{+}{\pi }^{-}$ and ${\pi }^{+}{\pi }^{-}$ atoms in proton–nucleus interactions at 450 GeV c(–)(1) and ${\theta }_{{\rm{lab}}}=4^\circ $ are estimated to be, respectively 67 ± 13, 31 ± 6 and 15 ± 2 times higher. [...]
DIRAC-PUB-2016-01.- 2016 - 17 p. - Published in : J. Phys. G 43 (2016) 095004

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2021-06-19
06:25
A new aerogel Cherenkov detector for DIRAC-II / Allkofer, Y (Zurich U.) ; Amsler, Claude (Zurich U.) ; Horikawa, S (Zurich U.) ; Regenfus, Christian (Zurich U.) ; Rochet, J (Zurich U.)
A new threshold Cherenkov detector using silica aerogel radiators is in operation in the DIRAC-II experiment at CERN. [...]
DIRAC-PUB-2008-03.
- 2008. - 4 p.

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2018-10-09
19:27
First measurement of a long-lived $\pi^+ \pi^-$ atom lifetime / DIRAC Collaboration
The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogen-like $\pi^+\pi^-$ 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;

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2017-06-13
09:51
Measurement of the $\pi K$ atom lifetime and the $\pi K$ scattering length / DIRAC Collaboration
After having announced the statistically significant observation (5.6~$\sigma$) of the new exotic $\pi K$ atom, the DIRAC experiment at the CERN proton synchrotron presents the measurement of the corresponding atom lifetime, based on the full $\pi K$ data sample: $\tau = (5.5^{+5.0}_{-2.8}) \cdot 10^{-15}s$. By means of a precise relation ($<1\%$) between atom lifetime and scattering length, the following value for the S-wave isospin-odd $\pi K$ scattering length $a_0^{-}~=~\frac{1}{3}(a_{1/2}-a_{3/2})$ has been derived: $\left|a_0^-\right| = (0.072^{+0.031}_{-0.020}) M_{\pi}^{-1}$..
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: PDF; Fulltext from publisher: PDF; Preprint: PDF;

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2016-04-29
23:54
Observation of $\pi^- K^+$ and $\pi^+ K^-$ atoms / DIRAC Collaboration
The observation of hydrogen-like $\pi K$ atoms, consisting of $\pi^- K^+$ or $\pi^+ K^-$ 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 APS Open Access article: PDF; Draft (restricted): PDF; Fulltext: CERN-EP-2016-128 - PDF; 10.1103_PhysRevLett.117.112001 - PDF; Preprint: PDF; External link: Fulltext

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2015-08-20
08:01
First observation of long-lived $\pi^+ \pi^-$ atoms / DIRAC collaboration
After observing and investigating the double-exotic $\pi^+\pi^-$ atom with the ground state lifetime $\tau$ of about $3 \times 10^{-15}$~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 $10^{-11}$~s and more. The number of characteristic pion pairs resulting from the breakup (ionisation) of long-lived $\pi^+\pi^-$ atoms amounts to $436\pm61$, 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; Preprint: PDF; External link: Preprint

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2015-06-10
21:18
Updated DIRAC spectrometer at CERN PS for the investigation of ππ and πK atoms / PS212 collaboration
The DIRAC spectrometer installed at CERN PS was redesigned and upgraded in order to study simultaneously Aππ and AπK atoms, namely the bound states of π+π–, and π+K–, π–K+ mesons. The detector system which is able to accept a high intensity beam such as 2 - 6 × 1011 primary protons per second, the electronics and the data-acquisition system adapted to handle very large amount of data actually allowed to identify successfully π, K, p, e and µ and to give the possibility to select π-π and π-K pairs in the off-line analysis. [...]
CERN-PH-EP-2015-147; DIRAC-PUB-2016-03.- Geneva : CERN, 2016 - 34 p. - Published in : Nucl. Instrum. Methods Phys. Res., A 839 (2016) 52-85 Draft (restricted): PDF; Fulltext: PDF;

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2014-08-20
07:34
New Preshower detector for DIRAC Experiment / Pentia, M. (Bucharest, IFIN-HH) ; Aogaki, S. (Bucharest, IFIN-HH) ; Dumitriu, D. (Bucharest, IFIN-HH) ; Fluerasu, D. (Bucharest, IFIN-HH) ; Gugiu, M. (Bucharest, IFIN-HH) ; Yazkov, V. (SINP, Moscow)
The Preshower (PSh) detector is a component of the DIRAC setup. It is designed to improve rejection efficiency of e-e+ pairs background in the {\pi}{\pi} and K{\pi} pair measurement. [...]
arXiv:1408.4246; DIRAC-PUB-2015-01.- 2015-09-21 - 6 p. - Published in : Nucl. Instrum. Methods Phys. Res., A 795 (2015) 200-205 Preprint: PDF; External link: Preprint

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2014-07-03
21:52
DIRAC observes dimeson atoms and measures their lifetime
Published in: CERN Courier Volume 52, Number 2, March 2012
Geneva : CERN, 2012

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2014-02-17
19:30
First $\pi K$ atom lifetime and $\pi K$ scattering length measurements / DIRAC Collaboration
The results of a search for hydrogen-like atoms consisting of $\pi^{\mp}K^{\pm}$ mesons are presented. Evidence for $\pi K$ atom production by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen in terms of characteristic $\pi K$ pairs from their breakup in the same target ($178 \pm 49$) and from Coulomb final state interaction ($653 \pm 42$). [...]
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; Elsevier Open Access article: PDF; Fulltext: PDF; Preprint: PDF; External link: Fulltext

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