ATLAS Event. IFAE 2011 Incontro di Fisica delle Alte Energie Perugia April Elvira Rossi. Università degli Studi di Napoli Federico II

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1 ATLAS Event sto IFAE 2011 Incontro di Fisica delle Alte Energie Perugia April 2011 J/!!"+"- ATLAS Event Elvira Rossi Università degli Studi di Napoli Federico II On behalf of ATLAS Collaboration Heavy Flavor1 Workshop - Purdue University, 6 January 2011 shop - Purdue University, 6 January

2 Outline Heavy Flavour Physics Programm and Motivation The ATLAS Detector J/ψ observation Measurements of J/ψ inclusive production and non-prompt to prompt cross-section Submitted Nuc. Phys. B Observation of Y system Exclusive B-meson decays ATLAS-CONF D mesons decays ATL-COM-PHY , ATLAS-CONF Summary IFAE April

3 Heavy Flavour Program at ATLAS Key elements for B-Physics searches: ² Efficient low pt muon trigger ² Very good: Muon coverage Track momentum resolution Mass resolution Vertex resolution Well understood MC L 0 fb 1 fb 1 1 fb 1 0 pb 1 pb 1 Rare decays Searches for new CP-violation in weak decays of B-mesons; rare decay searches; Λb polarization B-hadron properties, exclusive and inclusive B lifetimes Start rare decay activities: understand backgrounds - Detector & trigger understanding / calibration - J/ψ, Υ and exclusive B-channels - Early measurements of well known B and D- decays (production cross-section) LHC startup (Nov. 2009) Time IFAE April

4 Physics Motivation Main motivations for quarkonia studies at LHC: QCD physics uncertain hadron production mechanism unknown quarkonia polarization state But also: I. precise measurement of onia production allows to correctly subtract background for rare / interesting processes II. calibration and performance (in the low p T regime) measurement from data using a standard candle physics process both I and II need prompt to non-prompt separation capability, where nonprompt are J/ψ from decays of B hadrons IFAE April

5 Muon Spectrometer ( η <2.7) : air-core toroids with gas-based muon chambers Muon trigger and measurement with momentum resolution < % up to E µ ~ 1 TeV 3-level trigger reducing the rate from 40 MHz to ~200 Hz Inner Detector ( η <2.5, B=2T): Si Pixels, Si strips, Transition Radiation detector (straws) Precise tracking and vertexing, e/π separation Momentum resolution: σ/p T ~ 3.8x -4 p T (GeV) EM calorimeter: Pb-LAr Accordion e/γ trigger, identification and measurement E-resolution: σ/e ~ %/ E HAD calorimetry ( η <5): segmentation, hermeticity Fe/scintillator Tiles (central), Cu/W-LAr (fwd) Trigger and measurement of jets and missing E T E-resolution: σ/e IFAE ~ 50%/ E April

6 Muon reconstruction in ATLAS Combined Muons: Muons with an ID track matched to a MS track and refitted through the detector to give the best measurement. Tagged Muons: Muons w i t h a n I D t r a c k matched to a segment when extrapolated to the MS. Such muons generally have low momentum. IFAE April

7 Di-muon invariant mass spectrum Combined (Inner detector + Muon Spectrometer) opposite sign muons with: p T ( 1 ) > 15 GeV/c p T ( 2 ) > 2.5 GeV/c Display of a candidate J/ µµ event High Level Trigger (EF) with p T threshold of 15 GeV/c has been required IFAE April

8 J/ observation J/ events selection: Ø At least 1 primary vertex with 3 tracks associated Ø Quality cuts on the Inner Detector tracks to remove the badly measured muons Ø Opposite charge muon pairs with successful vertex fit. Ø One of the muon candidates needs to be combined Ø Momentum Cut: p T (µ 1 ) > 4 GeV p T (µ 2 ) > 2.5 GeV Ø (µ) < 2.5 J/ observation with L= 41pb measured mass and width in agreement with PDG M J/ = ± GeV ( m J/ ) = 65 ± 1 MeV IFAE April

9 J/ Differential Cross-Section Measurement Uses data collected between April and August 20 ² Maximum Likelihood fit of the J/ invariant mass in p T and y bins ² Each candidate is multiplied by in order to recover the true number of J/ µ + µ - events: Trigger efficiency extracted from data uses a data tag & probe method combined with MC for finer binning. Efficiency to reconstruct muon in the detector determined from data using a tag and probe method. IFAE April

10 J/ Differential Cross-Section Measurement: Acceptance Detector Acceptance depends strongly on the s p i n a l i g n m e n t, o r polarisation of the J/ n o t ( y e t ) m e a s u r e d under LHC conditions and will be an important future measurement. uncertainty in final measurement. dn dω =1+λ θ cos2 θ + λ φ sin 2 θ cos 2φ + λ θ φ sin 2θ cos φ 1 3 a a 0 2 2Re a +1a 1 1+ a 0 2 2Re [a 0 (a +1 a 1 )] 1+ a 0 2 Take 5 working points: C o v e r s m a x i m u m acceptance variations; applied as systematic uncertainty in final measurement. ATLAS CMS LHCb Moriond Electroweak Week Roger IFAE April 2011

11 Inclusive Differential CrossSection dy [nb/gev] /dp 2 µ - )d + Br(J/ µ Inclusive J/ production cross-section as a function of J/ transverse momentum in the rapidity bin 1.5 y <2. T ATLAS Preliminary s= 7 TeV = 2.27 pb L int Inclusive cross-section ATLAS 1.5 y <2 J/ CMS 1.6 y <2.4 J/ Spin-alignment envelope rapidity bin 1.5 y < J/ p [GeV] T Overlaid is a band representing the variation of the result under various spinalignment scenarios representing a theoretical uncertainty. The green points are the equivalent results from CMS. The measurements made by ATLAS and CMS are in good agreement with each other in the overlapping range of moderate p T values and complement each other at high (ATLAS) and low (CMS) values of transverse momenta. For more details see the poster J/ production cross section and non-prompt fraction IFAE April measurement with the ATLAS detector by Nicola Orlando

12 Prompt to Non-Prompt J/ Production Cross-Section Ratio Experimentally it is possible to distinguish between the J/ s from decay of heavier charmonium state (prompt production) from the J/ s produced via the decay of a B-hadron (non-prompt production). We define the prompt to non-prompt ratio R as: The pseudo-proper decay time separates prompt from non-prompt candidates: PseudoProperTime IFAE April

13 Non-Prompt Fraction J/ non-prompt fractions as a function of J/ transverse momentum Corrected J/ non-prompt cross-section as a function of J/ transverse momentum Non-prompt J/ production fraction ATLAS Preliminary = 2.44 pb L int ATLAS s=7 TeV, 1.5 y <2.0 J/ CMS s=7 TeV, 1.6 y <2.4 J/ Spin-alignment envelope rapidity bin 1.5 y <2 1 p J/ T [GeV] dy [nb/gev] T /dp non-prompt 2 µ - )d + Br(J/ µ 3 Non-prompt cross-section ATLAS 1.5 y <2.0 J/ 2 Spin-alignment envelope FONLL B J/ X ATLAS Preliminary s= 7 TeV = 2.44 pb L int rapidity bin 1.5 y <2 1 p J/ T [GeV] The yellow band represents the variation of the result under various spin-alignment scenarios representing a theoretical uncertainty. The green points are the equivalent results from CMS. Good agreement with the CMS results The error bars on the data points represent the combined statistical and systematic uncertainty. The luminosity uncertainty is not shown. Agreement is good with predictions IFAE April

14 Prompt Cross-Section Corrected inclusive J/ prompt cross-section as a function of J/ transverse momentum in the rapidity bin 1.5 y <2. dy [nb/gev] T /dp prompt 2 µ - )d + Br(J/ µ ATLAS Preliminary s= 7 TeV = 2.44 pb L int Prompt cross-section ATLAS 1.5 y <2.0 J/ Spin-alignment envelope Colour Evaporation Model NLO Colour Singlet NNLO* Colour Singlet rapidity bin 1.5 y < J/ p [GeV] T Predictions from the three models are superimposed. Overlaid is a band representing the variation of the result under various spin-alignment scenarios representing a theoretical uncertainty. The error bars on the data points represent the combined statistical and systematic uncertainty. The luminosity uncertainty is not shown. IFAE April

15 A heavy ion collision with a candidate J/ψà µ+µ- See the talk Studio della produzione di J/psi e Z in collisioni piombo piombo a LHC con l'esperimento ATLAS by Camilla MAIANI (ROMA1) IFAE April

16 Observation of the Upsilon System Observation of the three Upsilon resonances separated into detector regions of muons in: Barrel Barrel Endcap Barrel Endcap Endcap Muons were required to have p T > (2.5, 4) GeV and to be reconstructed within a < 2.5. Events / ( 0.1 GeV ) Endcap Endcap 3 8 ATLAS Preliminary s = 7 TeV L dt ~ 41.0 pb Data 20 : Opposite Sign Fit Projection Fit Projection of Background Endcap + Endcap N( 1S ) = ± 400 (stat.) N( 2S ) = 5500 ± 200 (stat.) N( 3S ) = 2000 ± 200 (stat.) Cross-section measurement in progress The signal lineshape fits are Gaussian with a fourth-order Chebyshev polynomial to model the background. The separations of the three peaks are fixed using the PDG masses but the absolute position on the invariant mass scale is allowed to float in the fit. Events / ( 0.1 GeV ) 5 3 Barrel Barrel ATLAS Preliminary s = 7 TeV L dt ~ 41.0 pb Data 20 : Opposite Sign Fit Projection Fit Projection of Background Barrel + Barrel N( 1S ) = ± 200 (stat.) N( 2S ) = 4800 ± 200 (stat.) N( 3S ) = 2300 ± 0 (stat.) Inv. M(µµ) [GeV] Events / ( 0.1 GeV ) ATLAS Preliminary s = 7 TeV L dt ~ 41.0 pb Inv. M(µµ) [GeV] Endcap Barrel Data 20 : Opposite Sign Fit Projection Fit Projection of Background Endcap + Barrel N( 1S ) = ± 200 (stat.) N( 2S ) = 3500 ± 200 (stat.) N( 3S ) = 1800 ± 200 (stat.) Inv. M(µµ) [GeV] IFAE April

17 Observation of B ± mesons: B ± J/ K o Dimuon in the J/ mass range combined with a third track (kaon mass assigned). o Fitted to a common vertex, with J/ mass constraint on dimuon Entries / (30 MeV) ATLAS Preliminary s = 7 TeV + J/ (µ µ )K + J/ (µ µ )K + L dt = 3.4 pb o Background suppression by applying a cut on transverse decay length Lxy > 0.3 mm Entries / (30 MeV) ATLAS Preliminary s = 7 TeV L dt = 3.4 pb m B ± = ± 2.5 (stat.) MeV = 39 ± 3 (stat.) MeV N B ± = 283 ± 22 (stat.) > 300 µm L xy 20 > 300 µm L xy m J/ K (MeV) Mass compatible with PDG value: M(B) = ± 2.5 MeV PDG: M(B) = ± 0.29MeV σ B = 39 ± 3 MeV N B = 283 ± m J/ K ± (MeV) ATLAS-CONF See also Charm and Beauty reconstruction IFAE in 2011 ATLAS April by A Ferretto Parodi 17

18 D-mesons production ü D mesons are produced in c and b fragmentation ü c and b quark production are hard processes (m Q >> QCD ) ü Theoretical calculations available up to NLO+NNLO level ü Still large theoretical uncertainties (scales, multiple interactions) Reconstruction of D-mesons already feasible with first ATLAS data due to: ² large cross section values ² clean D meson signatures ² precise ATLAS tracking and vertexing expected cc and bb cross sections in p-p collisions at s = 7 TeV: (cc ) 4.4 mb (bb) 0.24 mb first charm processes reconstructed in ATLAS: D* + D 0 π + (K - π + )π + (+c.c.) D + K - π + π + (+c.c.) D s + Φ π + (K - K + )π + (+c.c.) IFAE April

19 D-mesons production: D* D* + D 0 + (K - + ) + (+c.c.) Build D 0 signal from M(Kπ) for D* ± candidates Additional discrimination from mass difference ΔM = M(Kππ s )-M(Kπ) Use presence of secondary vertex and properties of hard process to guide cut selection to enhance signal ATLAS-CONF Mesons PDG Mass (MeV) ATLAS Mass (MeV) D* - D ± ± 0.05 D 0 IFAE April ± ± 1.419

20 D-mesons production: D s+ and D + D + s Φ π + (K - K + )π + (+c.c.) π + K + D + K - π + π+ (+c.c.) π + π + D s + Interaction Point Φ K - Secondary Vertex C (Ds + ) 150μm D+ Interaction Point K - Secondary Vertex C (D+) 312μm Mesons PDG Mass (MeV) ATLAS Mass (MeV) D ± ± ± 1.1 D s ± ± ± 4.6 ATLAS-CONF

21 B 0 d J/ K0* and B 0 s J/ Invariant mass distributions of reconstructed candidates of B 0 d J/ K0 * and anti-b 0 d J/ K0 * Invariant mass distributions of reconstructed B 0 s J/ candidates. The solid line is the projection of the result of the unbinned maximum likelihood fit to all candidates in the mass range from 5050 MeV to 5550 MeV. The solid line is the projection of the result of the unbinned maximum likelihood fit to all J/ ( + -) (KK) candidates in the mass range from 5150 MeV to 5600 MeV. The points with error bars are data. The solid line is the projection of the result of The dashed line is the projection for the background component of the fit. IFAE April

22 Summary and Outlook First year of data-taking has been highly successful Ø Observation of J/ and (2S). Ø Measurement performed of J/ differential crosssection and fraction of non-prompt to inclusive decays, prompt and non-prompt differential cross-sections. Ø Observation of the three Upsilon states. Ø D meson states observed and cross section measued. Ø Observation of B ± J/ ( )K ±, B d J/ ( )K* 0 and B s J/ ( ) Short and longer term plans include v Exclusive decays like B c J/ ( ) v Continue preparations for searches on rare decays such as B s and beyond promises bring many more enthusiastic results IFAE April