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Author |
LHCb Collaboration (Aaij, R. et al); Jashal, B.K.; Martinez-Vidal, F.; Oyanguren, A.; Remon Alepuz, C.; Ruiz Vidal, J. |
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Title |
Observation of an exotic narrow doubly charmed tetraquark |
Type |
Journal Article |
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Year |
2022 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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Volume |
18 |
Issue |
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Pages |
751-754 |
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Keywords |
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Abstract |
Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark-antiquark pair, respectively(1,2). Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a (u) over bar and a (d) over tilde quark. This exotic state has a mass of approximately 3,875 MeV and manifests as a narrow peak in the mass spectrum of (DD0)-D-0 pi(+) mesons just below the D*D-+(0) mass threshold. The near-threshold mass together with the narrow width reveals the resonance nature of the state. |
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Address |
[Aaij, R.; Butter, J. S.; Akiba, K. Carvalho; Sole, S. Ferreres; Gabriel, E.; Geertsema, R. E.; Greeven, L. M.; Heijhoff, K.; Hulsbergen, W.; Hynds, D.; Jans, E.; Ketel, T.; Klaver, S.; Koppenburg, P.; Kostiuk, I; Kuindersma, H. S.; Martinez, M. Lucio; Lukashenko, V; Mauri, A.; Merk, M.; Pellegrino, A.; Raven, G.; Gras, C. Sanchez; Schubiger, M.; Soares, M. Senghi; Snoch, A.; Tuning, N.; Usachov, A.; Van Beuzekom, M.; Veronesi, M.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands |
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Nature Portfolio |
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English |
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Series Volume |
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Edition |
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ISSN |
1745-2473 |
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Conference |
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Notes |
WOS:000811954400004 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5279 |
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Permanent link to this record |
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Author |
LHCb Collaboration (Aaij, R. et al); Jashal, B.K.; Martinez-Vidal, F.; Oyanguren, A.; Remon Alepuz, C.; Ruiz Vidal, J. |
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Title |
Study of the doubly charmed tetraquark T-cc(+) |
Type |
Journal Article |
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Year |
2022 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Commun. |
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Volume |
13 |
Issue |
1 |
Pages |
3351 - 19pp |
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Keywords |
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Abstract |
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the (DD0)-D-0 pi(+) mass spectrum just below the D*+D-0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T-cc(+), tetraquark with a quark content of cc (u) over bar(d) over bar and spin-parity quantum numbers J(P) =1(+). Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*(+) mesons is consistent with the observed D-0 pi(+) mass distribution. To analyse the mass of the resonance and its coupling to the DID system, a dedicated model is developed under the assumption of an isoscalar axial-vector T-cc(+), state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T-cc(+), state. In addition, an unexpected dependence of the production rate on track multiplicity is observed. |
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Address |
[Aaij, R.; Butter, J. S.; Akiba, K. Carvalho; Sole, S. Ferreres; Gabriel, E.; Geertsema, R. E.; Greeven, L. M.; Heijhoff, K.; Hulsbergen, W.; Hynds, D.; Jans, E.; Ketel, T.; Klaver, S.; Koppenburg, P.; Kostiuk, I; Kuindersma, H. S.; Martinez, M. Lucio; Lukashenko, V; Mauri, A.; Merk, M.; Pellegrino, A.; Raven, G.; Gras, C. Sanchez; Schubiger, M.; Soares, M. Senghi; Snoch, A.; Tuning, N.; Usachov, A.; van Beuzekom, M.; Veronesi, M.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands, Email: Ivan.Belyaev@cern.ch |
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Nature Portfolio |
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English |
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Conference |
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Notes |
WOS:000812556800001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5280 |
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Permanent link to this record |
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Author |
LHCb Collaboration (Aaij, R. et al); Henry, L.; Jashal, B.K.; Martinez-Vidal, F.; Oyanguren, A.; Remon Alepuz, C.; Ruiz Vidal, J. |
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Title |
Precise determination of the B-s(0)-B-s(-0) oscillation frequency |
Type |
Journal Article |
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Year |
2022 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
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Volume |
18 |
Issue |
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Pages |
54-58 |
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Keywords |
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Abstract |
Mesons comprising a beauty quark and strange quark can oscillate between particle (B-s(0)) and antiparticle (B-s(-0)) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Delta m(s). Here we present a measurement of Delta m(s) using B-s(0) -> D-s(-)pi(+) decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Delta m(s) = 17.7683 +/- 0.0051 +/- 0.0032 ps(-1), where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Delta m(s) precision by a factor of two. We combine this result with previous LHCb measurements to determine Delta m(s) = 17.7656 +/- 0.0057 ps(-1), which is the legacy measurement of the original LHCb detector. |
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Address |
[Aaij, R.; Butter, J. S.; Akiba, K. Carvalho; Sole, S. Ferreres; Gabriel, E.; Geertsema, R. E.; Greeven, L. M.; Heijhoff, K.; Hulsbergen, W.; Hynds, D.; Jans, E.; Klaver, S.; Koppenburg, P.; Kostiuk, I; Kuindersma, H. S.; Martinez, M. Lucio; Lukashenko, V; Mauri, A.; Merk, M.; Pellegrino, A.; Sanchez Gras, C.; Schubiger, M.; Snoch, A.; Tuning, N.; Usachov, A.; van Beuzekom, M.; Veronesi, M.] Nikhef Natl Inst Subatom Phys, Amsterdam, Netherlands, Email: alessandro.bertolin@pd.infn.it |
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Nature Portfolio |
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English |
Summary Language |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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ISSN |
1745-2473 |
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Conference |
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Notes |
WOS:000739810100002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5075 |
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Permanent link to this record |
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Author |
LHCb Collaboration (Aaij, R. et al); Jashal, B.K.; Martinez-Vidal, F.; Oyanguren, A.; Remon Alepuz, C.; Ruiz Vidal, J. |
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Title |
Evidence for a New Structure in the J/psi p and J/psi(p)over-bar Systems in B-s(0) -> J/psi p(p)over-bar Decays |
Type |
Journal Article |
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Year |
2022 |
Publication |
Physical Review Letters |
Abbreviated Journal |
Phys. Rev. Lett. |
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Volume |
128 |
Issue |
6 |
Pages |
062001 - 11pp |
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Keywords |
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Abstract |
An amplitude analysis of flavor-untagged B-s(0) -> J=psi p (p) over bar decays is performed using a sample of 797 +/- 31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 fb(-1). Evidence for a new structure in the J=psi p and J=psi(p) over bar systems with a mass of 4337(-4-2)(+7+2) MeV and a width of 29(-12-14)(+26+14) MeV is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7 sigma, depending on the assigned J(P) hypothesis. |
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Address |
[Aaij, R.; Leite, J. Baptist; Bediaga, I; Torres, M. Cruz; De Miranda, J. M.; Dos Reis, A. C.; Gomes, A.; Massafferri, A.; Machado, D. Torres] Ctr Brasileiro Pesquisas Fis CBPF, Rio De Janeiro, Brazil |
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Publisher |
Amer Physical Soc |
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English |
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0031-9007 |
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Notes |
WOS:000759202300001 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5157 |
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Permanent link to this record |
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Author |
Aarrestad, T. et al; Mamuzic, J.; Ruiz de Austri, R. |
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Title |
Benchmark data and model independent event classification for the large hadron collider |
Type |
Journal Article |
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Year |
2022 |
Publication |
Scipost Physics |
Abbreviated Journal |
SciPost Phys. |
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Volume |
12 |
Issue |
1 |
Pages |
043 - 57pp |
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Keywords |
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Abstract |
We describe the outcome of a data challenge conducted as part of the Dark Machines (https://www.darkmachines.org) initiative and the Les Houches 2019 workshop on Physics at TeV colliders. The challenged aims to detect signals of new physics at the Large Hadron Collider (LHC) using unsupervised machine learning algorithms. First, we propose how an anomaly score could be implemented to define model-independent signal regions in LHC searches. We define and describe a large benchmark dataset, consisting of > 1 billion simulated LHC events corresponding to 10 fb(-1) of proton-proton collisions at a center-of-mass energy of 13 TeV. We then review a wide range of anomaly detection and density estimation algorithms, developed in the context of the data challenge, and we measure their performance in a set of realistic analysis environments. We draw a number of useful conclusions that will aid the development of unsupervised new physics searches during the third run of the LHC, and provide our benchmark dataset for future studies at https://www.phenoMLdata.org. Code to reproduce the analysis is provided at https://github.com/bostdiek/DarkMachines-UnsupervisedChallenge. |
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Address |
[Aarrestad, Thea; Heinrich, Lukas A.; Jawahar, Pratik; Pierini, Maurizio; Touranakou, Mary; Wozniak, Kinga A.] European Org Nucl Res CERN, CH-1211 Geneva 23, Switzerland |
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Publisher |
Scipost Foundation |
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English |
Summary Language |
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Original Title |
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Series Editor |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
2542-4653 |
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Notes |
WOS:000807448000038 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5256 |
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Permanent link to this record |