Measurement ofD0–D¯0Mixing Parameters and Search forCPViolation UsingD0→K+π−Decays

R Aaij,T M Karbach,T Lesiak,S Gregson,J M Otalora Goicochea,S Stoica,G Raven,P Garosi,C Wallace,O Okhrimenko,B Rachwal,C Pavel-Nicorescu,G Penso,V Romanovsky,C Coca,G Veneziano,O Yushchenko,Y Shcheglov,M Tresch,A Affolder,R Schwemmer,E Pesen,B Souza De Paula,E Tournefier,B Storaci,P Ilten,R J Barlow,S C Haines,C Frei,W Baldini,T Hartmann,N K Watson,U Eitschberger,A Grecu,B Spaan,I Longstaff,P David,R Bernet,M.-N Minard,S T Harnew,G Ciezarek,Y Li,W Kanso,A Richards,R Oldeman,R Silva Coutinho,S Farry,V Egorychev,N Neufeld,K Ciba,F Kruse,L Pescatore,M Veltri,L De Paula,J M De Miranda,D Dossett,G D Patel,F Bedeschi,L Shekhtman,A Massafferri,S Reichert,B K Pal,A Kozlinskiy,M D Sokoloff,T Shears,T Bird,L Carson,L Grillo,B Popovici,S Hall,J He,R Lefèvre,E Graugés,S Wandernoth,G Sabatino,D A Roberts,M Nicol,M Artuso,R Nandakumar,S Swientek,F Machefert,A B Rodrigues,M Calvi,U Marconi,J Lefrançois,R Le Gac,K Hennessy,M Kaballo,M Calvo Gomez,V Pugatch,P M Bjørnstad,S Topp-Joergensen,C Göbel,V Bocci,C Linn,A Borgia,D A Milanes,J Wiechczynski,T Kvaratskheliya,V Niess,D Golubkov,C Farinelli,N Rauschmayr,G Graziani,G Mancinelli,W Bonivento,C Langenbruch,B Pietrzyk,A Romero Vidal,A Nomerotski,R Dzhelyadin,W C Zhang,M Clemencic,H Dijkstra,E Greening,P Owen,G Auriemma,M Schmelling,J Maratas,R Forty,H V Cliff,M Szczekowski,S Ricciardi,B Jost,E Hicks,Ph Charpentier,P Spradlin,A Carbone,M Adinolfi,A Zvyagin,R Lindner,F Teubert,L Li Gioi,A Schopper,M Sapunov,T Nikodem,B Mcskelly,M Alexander,A Falabella,V Gibson,A Semennikov,F Dupertuis,C Satriano,M Karacson,M Heß,A Phan,F Muheim,O Callot,S Oggero,D Ferguson,B Rakotomiaramanana,G Alkhazov,A Jawahery,A Sciubba,C Matteuzzi,Y Xie,G Corti,L A Granado Cardoso,R Mcnulty,S Amerio,C Voß,S Coquereau,R Cardinale,A Leflat,P Seyfert,U Egede,E Teodorescu,D Hutchcroft,A Mazurov,K Wyllie,B Sanmartin Sedes,D A Roa Romero,E Gersabeck,L Zhong,S Lohn,M Van Beuzekom,C Lazzeroni,A Vorobyev,G Carboni,J Panman,P Koppenburg,M Williams,T J V Bowcock,A Powell,M Palutan,F Zhang,M Pappagallo,M Patel,P Morawski,N Bondar,P E L Clarke,O Maev,M T Tran,P Tsopelas,A Contu,O Lupton,S Bachmann,O Aquines Gutierrez,P Szczypka,I Sepp,D Wiedner,T Szumlak,P Marino,F Meier,A Camboni,C Hombach,J Cogan,V Shevchenko,S Perazzini,R B Appleby,S Borghi,T Britton,M Teklishyn,P Durante,A Dovbnya,A Lai,B Viaud,T Gys,M Witek,M Deckenhoff,A Zhokhov,A C Dos Reis,U Uwer,H Schindler,W Qian,S Malde,M Britsch,R Santacesaria,X Yuan,R Niet,P Gandini,L Garrido,S Roiser,N Sagidova,Y Zhang,A Puig Navarro,P Sail,L Eklund,C Vázquez Sierra,O Schneider,G Manca,K De Bruyn,A Papanestis,T Hampson,F Dordei,R F Koopman,K Senderowska,Ch Cauet,B Meadows,P Hunt,C Hadjivasiliou,M De Cian,A Pearce,V Vagnoni,J Prisciandaro,S Cunliffe,A Zhelezov,A Ukleja,R Currie,Ph Ghez,D Savrina,R Wallace,J Harrison,I Shapoval,D Websdale,R Vazquez Gomez,A Cook,E Thomas,D Moran,L Kravchuk,A Di Canto,A A Alves,G Martellotti,V Fernandez Albor,M Cruz Torres,E Lanciotti,A Sparkes,F Polci,G A Cowan,D Brett,M Pepe Altarelli,E Ben-Haim,I El Rifai,D Voong,A Tsaregorodtsev,R Märki,Yu Guz,V Tisserand,N Skidmore,H Voss,P Krokovny,K Müller,M P Williams,F Fontanelli,V K Subbiah,S Filippov,S De Capua,F Soomro,C Färber,M Smith,C Adrover,C Potterat,J Garofoli,S Redford,A D Nguyen,I R Kenyon,A Martín Sánchez,R Matev,G Polok,A Popov,M S Rangel,J Blouw,C R Jones,I Komarov,A Gomes,A Golutvin,M Needham,J Luisier,M Zangoli,M Hoballah,J Anderson,A Ustyuzhanin,C Patrignani,L Sun,D Hynds,P Campana,D Van Eijk,O Steinkamp,A Oyanguren,M Seco,A Pritchard,J Wicht,C Joram,A Cardini,P Perret,T Huse,A D Webber,R Cenci,G Krocker,B Gui,I Mous,S Tourneur,V Kudryavtsev,H Luo,S Leo,L Giubega,G Passaleva,E Picatoste Olloqui,J H Lopes,L Del Buono,D Martins Tostes,S Blusk,Th Bauer,A Martens,R Mountain,A Vollhardt,M Meissner,J Van Leerdam,G Punzi,C Fitzpatrick,S Amato,M Zavertyaev,G Bencivenni,A Gallas Torreira,N Chiapolini,M Idzik,S Monteil,E Jans,S Donleavy,E Furfaro,M Frosini,I V Machikhiliyan,M Rotondo,V V Gligorov,M J Morello,C Baesso,J Benton,S A Wotton,C Thomas,A Poluektov,A Palano,L Anderlini,T Ruf,M Kucharczyk,M John,S Easo,J Wimberley,H Ruiz,V Rives Molina,O Kochebina,G Valenti,M Liles,A Martynov,X Cid Vidal,S Hansmann-Menzemer,A Pérez-Calero Yzquierdo,A Vallier,L Wiggers,C Haen,M Cattaneo,D Vieira,J E Andrews,E Aslanides,A Petrolini,K Carvalho Akiba,M Schlupp,A Badalov,M M Reid,M Gandelman,R Ekelhof,A Satta,H Brown,M Grabalosa Gándara,A Jaeger,G N Patrick,J Wishahi,R Jacobsson,T Head,A Novoselov,D Campora Perez,R Graciani Diaz,M Dogaru,K Belous,J Rouvinet,U Straumann,M Perrin-Terrin,C Nguyen-Mau,C Parkes,J J Saborido Silva,J Bressieux,J Closier,G Haefeli,S Stevenson,W Sutcliffe,S Eidelman,A Hicheur,V Syropoulos,A Dosil Suárez,C Bozzi,P Alvarez Cartelle,P Ruiz Valls,R Andreassen,D C Craik,E Santovetti,F Dettori,S Wright,T Brambach,N Harnew,O Grünberg,P Naik,A Bursche,G Wormser,T D Nguyen,T Ketel,G Pessina,Y Gao,F Stagni,W Hulsbergen,S Vecchi,J J Back,M Shapkin,C Barschel,B Couturier,B 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Albrecht,A Berezhnoy,J Buytaert,Y Amhis,M Gersabeck,A Bondar,F Jing,A Mcnab,G Casse,T Gershon,T Skwarnicki,V Coco,J H Rademacker,J J Velthuis,B Liu,T Nakada,Z Yang,S Stahl,J Smith,K Petridis,A Sarti,O Deschamps,F Alessio,M Fontana,P Robbe,S Cadeddu,D Popov,K Rinnert,B Adeva,C J Parkinson,R Waldi,W Barter,S Stone,M Charles,A Comerma-Montells,M Martinelli,S Barsuk,S Wu,E Smith,B Khanji,A Pellegrino,S Benson,B Sciascia,S T’Jampens,C D’Ambrosio,L Zhang,Ch Elsässer ,A Pazos Álvarez ,Z Máthé ,X Vilasis‐Cardona ,A Obłąkowska-Mucha ,C Prouvé ,C Santamarina Ríos ,J Garra Ticó ,M Ferro‐Luzzi ,R Mureşan ,N López-March ,O De Aguiar Francisco ,О Shevchenko ,A Bień ,E Pérez Trigo ,D Décamp ,M Pló Casasús ,А Артамонов ,M H Schune ,P A Gorbounov ,D Lacarrère ,N Smith ,Robert Lambert ,P Vázquez Regueiro ,M Chrząszcz ,J P Lees ,P J Dornan ,H Lü ,Д Деркач ,N Déĺeage ,H A Gordon ,G D Lafferty ,V Salustino Guimarães ,M Savrié ,P Rodríguez Pérez ,D Martínez Santos ,M O Bettler ,S F Cheung ,М Королев ,В Яковенко ,W Wiślicki ,L Castillo García ,S Eisenhardt,T Latham,M Frank,O Leroy,M Kreps,E Maurice,J Wang,V Balagura,N Nikitin,J Van Den Brand

doi:10.1103/physrevlett.111.251801

Abstract

Measurements of charm mixing parameters from the decay-time-dependent ratio of D0->K+pi- to D0->K-pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb^{-1} of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x'^2=(5.5 +- 4.9)x10^{-5}, y'= (4.8 +- 1.0)x10^{-3}, and R_D=(3.568 +- 0.066)x10^{-3}. Allowing for CP violation, the mixing parameters are determined separately for D0 and D0bar mesons yielding A_D = (-0.7 +- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < |q/p|< 1.24 at the 68.3% confidence level, where q and p are parameters that describe the mass eigenstates of the neutral charm mesons in terms of the flavor eigenstates. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.

Highlights

Mass eigenstates of neutral charm mesons are linear combinations of flavor eigenstates jD1;2i1⁄4pjD0iÆqjD" 0i, where p and q are complex parameters
If CP symmetry is violated, the oscillation rates for mesons produced as D0 and D" 0 can differ, further enriching the phenomenology
The study of CP violation in D0 oscillation may lead to an improved understanding of possible dynamics beyond the standard model [4,5,6,7]

Summary

RD þ

Where t is the decay time, is the average D0 lifetime, and RD is the ratio of suppressed-to-favored decay rates. A WS candidate is discarded if resulting from a D0 candidate that, associated with another pion, forms a RS candidate with MðD0þs Þ within 3 MeV=c2 of the known DÃþ mass This removes about 15% of the WS background with negligible signal loss. The two subsamples contribute approximately equal signal yields with similar purities They require separate treatment due to their differing kinematic distributions and trigger-induced biases. These are corrected for the relative efficiencies for reconstructing KÀþ and KþÀ final states

No CPV

Findings

Xrþi i