Beauty 03 Eerola

Slide1: 

ATLAS B Physics Performance Update ﴀPaula Eerola for the ATLAS Collaboration Beauty 2003, Carnegie Mellon 14-18 Oct 2003 Detector and trigger Precision measurements Rare decays B production Summary

Slide2: 

Unlike BaBar, Belle, access to Bs and Lb decays (BsKK, BsDsK, BsJ/yf (h) , Lb J/yL. . .) Mixing measurements Much higher statistics than at the Tevatron Access to rare b-decays (BdK* g, BdK*mm, Bsmm . . .) Precision CPV measurements (Bd J/y K0S. . .) NP? b d d b t t High statistics is a requirement New particles may show up in loop diagrams, overconstrain will allow to disentangle SM components from the new-physics ones Bd Bs B decays at LHC

B production at LHC: 

B production at LHC ATLAS/CMS and LHCb are complementary

The ATLAS Detector: 

The ATLAS Detector The Inner Detector (ID): pixels, silicon detectors and the transition radiation tracker inside a solenoidal 2T field (see H. G. Moser) + Good tracking – complementary systematics to the LHCb case + e/p separation in TRT - marginal p/K identification ID, calorimeters and muon system cover |h|andlt;2.5 + Access to central region good for production studies Muon trigger and reconstruction down to pT=5 (3) GeV in muon chambers, tile calorimeter, ID. Electron trigger and reconstruction down to pT=2 GeV in LAr calorimeter, TRT (see S. George) + Better statistics than LHCb in all leptonic channels + Very good for leptonic rare decays (high luminosity running) - Must share trigger bandwidth with other physicshadronic channels suffer

ATLAS construction: 

ATLAS construction Installation status: installation activities at LHC Point 1 have started. April 2003: part of the underground experimental area (UX15) has been delivered to ATLAS. Nov 2003: start installing feet and rails. All subdetectors are under construction, some already completed (tile calorimeter). Jan 2004 first detector parts in the cavern: barrel calorimeter, tile calorimeter first, then LAr. Mar 2004 barrel toroid coils. The 'initial' detector ready for global commissioning and cosmics summer 2006, ready for beam in April 2007. Some components will be staged for later installation. Shielding installation in the underground cavern, status 2003. Engineering simulation: the Barrel Toroid and the Barrel Calorimeter installed in position (October 2004).

Slide6: 

ATLAS initial detector Proper time resolution for Bs decays (TDR layout): core resolution 52 fs. Initial layout: core resolution andgt; 60 ps, cuts to be optimized in view of Dms measurement (N(events) vs resolution). Initial and complete layouts have appr. the same t- resolution (fewer detector layers andgt;andlt; less material). Decay time resolution Bs  Ds(f p) p

Slide7: 

The ATLAS Trigger will consist of three levels 40 MHz  Level-1  O(20 kHz)  Level-2  O(1-5 kHz)  Event Filter  O(200 Hz). B-physics ‘classical’ scenario: LVL1 muon with pT andgt; 6 GeV, || andlt; 2.4, LVL2 muon confirmation, ID full scan. The B-physics trigger strategy had to be revised changed LHC luminosity target (1  21033 cm-2s-1) changes in detector geometry, possibly reduced detector at start-up tight funding constraints Alternatives to reduce resource requirements require at LVL1, in addition to single-muon trigger, a second muon, a Jet or EM RoI; reconstruct tracks at LVL2 and EF within RoI flexible trigger strategy: start with a di-muon trigger for higher luminosities, add further triggers (hadronic final states, final states with electrons and muons) and/or lower the thresholds later in the beam-coast/for low-luminosity fills. B-Physics Trigger

Slide8: 

New Scenario: B-physics trigger types (always single muon at LVL1) di-muon trigger: additional muon at LVL1. Effective selection of channels with J/(+-), rare decays like B  +-(X), etc. hadronic final states trigger : RoI-guided reconstruction in ID at LVL2, RoI from LVL1 Jet trigger. Selection of hadronic modes e.g. Bs  Ds p electron-muon final states trigger: RoI-guided reconstruction in TRT at LVL2, RoI from LVL1 EM trigger. Selection of electrons, e.g. J/y e+e- ‘classical’ scenario as fall-back Results are promising Strong reduction in processing requirements compared to previous strategy that involved full scan of Inner Detector at level-2. Further studies needed. B-Physics Trigger II

Precision measurements: sin2b, a: 

Precision measurements: sin2b, a sin2b measurement with BdJ/yK0S. Maximum likelihood fit with simulated inputs: proper time resolution, tag probability, wrong tag fraction, background composition. Direct CP violation term neglected here. TDR layout. Sensitivity to angle a: fit (Adircos(Dm t) + Amixsin(Dm t)) in Bhh. Adir, Amix in SM depend on a, d (or aeff), O(|P/T|2). ATLAS alone: s(Adir)=0.16, s(Amix)=0.21  combined LHC measurement.

Precision measurements: B0s: 

Precision measurements: B0s Dms measured from flavour specific final states Bs  Ds p and Bs Ds a1 . Already after 1 year (10 fb-1) sensitivity to Dms up to 36 ps-1  SM allowed range Dms (14.3 - 26) ps-1 fully explored. Precise measurements of B0s- anti-B0s system parameters : DGs, Dms. Probe Bs mixing phase fs= -2l2h to investigate new physics.

Slide11: 

Standard Model region-updated 2003 New physics Left-right symmetric model (NP-LR) - updated 2000. fs from J/yf: ATLAS (3 years). TDR detector. Same as above with complete detector layout – Preliminary. fs from J/yf: LHCb(5 years). Performance parameters as 2000 fs from J/yh: ATLAS (3 years). DGs and fs from B0sJ/yf (h) DGs, Gs and fs determined from angular analyses of Bs  J/y (mm)f(KK). DGs can be determined with a relative error of 12% (stat) with 30 fb-1. Measurement precision of fs depends on xs: for Bs  J/yf, sensitivity in the range 0.08-0.15 for xs=20-40 (SM) (Dms = 13.7-27.3 ps-1) Bs  J/yh: sensitivity for fs in the range 0.27-0.31 for xs=20-30 (Dms = 13.7-20.5 ps-1)

Slide12: 

The expected large production rates at the LHC will allow for precision measurements of Bc properties recent estimates for ATLAS (assuming f(b  Bc)~10-3, 20 fb-1, LVL1 muon with pT andgt; 6 GeV, || andlt; 2.4) ~5600 Bc  J/  produced events ~100 Bc  Bs  produced events Channels studied so far: Bc  J/  (mass measurement), Bc  J/  (clean signature, ingredient for |Vcb| determ.) MC generation of Bc events using standard tools is CPU intensive. Implementation of two MC generators in PYTHIA 6.2 Fragmentation Approximation Model MC Full Matrix Element MC (C. Driouichi et al., hep-ph/0309120): based on the 'extended helicity' approach (grouping of Feynman diagrams into gauge-invariant sub-groups to simplify calculations, never done for gg  QQ before). pQCD to O(s4), 36 diagrams contributing. Bc Studies in ATLAS

Slide13: 

Results from FME generator (BCVEGPY 1.0) Bc Studies in ATLAS II pseudo-rapidity rapidity Bc Bc*

Slide14: 

First preliminary results from full detector simulation (Geant3) and reconstruction ‘initial layout’ channel Bc  J/  mass resolution Bc= 74 MeV Bc Studies in ATLAS III Fast simul. mass resolution J/ = 41 MeV

Rare decays B0s,dm+m-: 

Rare decays B0s,dm+m- Bs,dmm: BR=3.5x10-9 (Bs) and 1.5x10-10 (Bd) (SM, 'optimistic') clear signature, tiny BR  ideal for new physics observation. Di-muon trigger allows high-luminosity data-taking. After 1 year at high luminosity (100 fb-1) – 4.3s signal After 1 year 1034cm-2 s-1 The difference with CMS can be attributed to better vertex reconstruction precision and secondary vertex selection. There is an indication of possible improvement of background conditions with another vertex fit procedure. FCNC B decays with bs or bd occur only at loop level in SM BR andlt; 10-5  probe of new physics

Rare decays B0s,dm+m-X: 

Lowest mass region: sufficient accuracy to separate SM and MSSM if Wilson coefficient C7g andlt;0 Three points: mean values of AFB in three q2/MB2 experimental regions with error bars Rare decays B0s,dm+m-X BdK*mm: sensitive to |Vts| . The shape of F-B asymmetry is sensitive to new physics (MSSM) N(Bdrmm)/N(BdK*mm)~ |Vtd|2/|Vts|2 useful also for ms/md estimation – complementary to oscill.meas. Statistics with 30 fb-1

Rare decays B0  K0* g: 

BR( B0  K0* g ) = (4.20.4) 10-5 Sensitive to New Physics effects through the loop diagram Rare decays B0  K0* g 2.8% rec. efficiency (incl. muon efficiency)  statistics 10 500 events per 30 fb-1 . Combinatorial background from bbm(6)X was considered. Specific background from B0K*p0 is under investigation. 57 MeV mass resolution

B production at LHC: 

CDF ATLAS/CMS Bjorken x region: one of B’s in detector volume: LHCb most sensitive to knowledge of structure functions at very low x LHCb CDF and D0 beauty cross section in central region underestimated by NLO QCD by ~2.4 Better agreement at higher pT (D0 measurement with b-jets) B production at LHC

B production at LHC II: 

CDF measurement of b-b correlations using m + jet data LHC statistics will allow using exclusive channels instead of b-jets Pythia is above the data NLO QCD is below the data B production at LHC II

B production at LHC III: 

Bm Bd  J/yKs0 Bm Bs  J/yf ATLAS - proposal for measuring b-b production correlations using exclusive B-decays and semileptonic decays to muons No degradation of efficiency as b-b close in space. In Bs case – interesting specific background Km originating from s-quark associated with Bs production. Need Be Bs  J/yf Df=f J/y - fm B production at LHC III

Lb production polarization: 

In p-p collisions Lb baryon will be polarized perpendicularly to production plane. The polarization vanishes as h 0 because of p-p symmetry. At LHCb polarization higher than ATLAS/CMS. Lb q1 q2 p p p p f2 n q q1 Angular distribution Lb J/y(mm)L(pp) depends on 5 angles (fig) + 6 parameters of 4 helicity amplitudes and polarization Pb . Helicity amplitudes and Pb – simultaneously determined. 75000 Lb J/y(mm)L(pp) in 3 years will allow precision dPb = 0.016. Also studied Properties of beauty baryons. Lb production polarization

Conclusions: 

Conclusions ATLAS is preparing a multithematic B-physics program. Includes B-decays and B-production. ATLAS B-physics trigger strategy revised to maximize physics potential within tight funding constraints: Rely on dimuon trigger for initial luminosity 2  1033 cm-2s-1, extending the selection when the luminosity falls. The main emphasis will be on underlying mechanisms of CP violation and evidence of New physics. ATLAS is especially precise in measurement of angle b. In Bs  J/y f(h) large CP violation would indicate new physics. There is sensitivity to Dms beyond SM expectations. The expected large production rates at the LHC will allow for precision measurements of Bc properties: e.g. ~5600 Bc  J/  produced events, ~100 Bc  Bs  prod. events Rare decays B  mm(X) have a favourable experimental signature, allowing measurements also at the nominal LHC luminosity 1034 cm-2s-1. Will measure branching ratio of Bs  mm which is in SM of order Brandlt;(10-9) Precision measurements will be done for B  K*mm. Large sample of BK*g allows for probing New physics effects. Beauty production and bb correlations in central LHC collisions will be measured for QCD tests. Complementary phase space region to LHCb.

Backup slides: 

Backup slides

Slide24: 

Reconstruction of masses

Slide25: 

Armin NAIRZ Heavy Quarkonium Workshop, FNAL, September 20-22, 2003 8 Di-muon trigger effective selection of channels with J/(+-), rare decays like B  +-(X), etc. minimum possible thresholds: pT andgt; 5 GeV (Muon Barrel) pT andgt; 3 GeV (Muon End-Cap) actual thresholds determined by LVL1 rate at LVL2 and EF: confirmation of muons using the ID and Muon Precision Chambers at EF mass and decay-length cuts, after vertex reconstruction trigger rates (21033 cm-2s-1): ~200 Hz after LVL2, ~10 Hz after EF B-Physics Trigger III

Slide26: 

ATLAS initial detector

Slide27: 

Software andamp; physics channels

Slide28: 

B-hadrons — proper time resolution V.M. Ghete, E. Bouhova, P. Reznicek, M. Smizanska, B. Epp, S. Sivoklokov, N. Nikitine, K. Toms

Slide29: 

The ATLAS Trigger will consist of three levels Level-1 (40 MHz  O(20 kHz)) muons, Regions-of-Interest (RoI’s) in the Calorimeters B-physics (‘classical’ scenario): muon with pT andgt; 6 GeV, || andlt; 2.4 Level-2 (O(20 kHz)  O(1-5 kHz)) RoI-guided, running dedicated on-line algorithms B-physics (‘classical’ scenario): muon confirmation, ID full scan Event Filter (O(1-5 kHz)  O(200 Hz)) offline algorithms, alignment and calibration data available The B-physics trigger strategy had to be revised changed LHC luminosity target (1  21033 cm-2s-1) changes in detector geometry, possibly reduced detector at start-up tight funding constraints B-Physics Trigger

Slide30: 

Alternatives to reduce resource requirements require at LVL1, in addition to single-muon trigger, a second muon, a Jet or EM RoI, reconstruct at LVL2 and EF within RoI re-analyse thresholds and use flexible trigger strategy start with a di-muon trigger for higher luminosities add further triggers (hadronic final states, final states with electrons and muons) later in the beam-coast/for low-luminosity fills B-physics trigger types (always single muon at LVL1) di-muon trigger: additional muon at LVL1. Effective selection of channels with J/(+-), rare decays like B  +-(X), etc. hadronic final states trigger : RoI-guided reconstruction in ID at LVL2, RoI from LVL1 Jet trigger. Selection of hadronic modes e.g. Bs  Ds p electron-muon final states trigger: RoI-guided reconstruction in TRT at LVL2, RoI from LVL1 EM trigger. Selection of electrons, e.g. J/y e+e- ‘classical’ scenario as fall-back Results are promising Strong reduction in processing requirements compared to previous strategy that involved full scan of Inner Detector at level-2. Further studies needed. B-Physics Trigger II

Slide31: 

The current theoretical uncertainty on |P/T|, s|P/T|~30%, dominates other systematical and statistical errors of full LHC potential. a-sensitivity as a function of a and theoretical uncertainty of |P/T| using full LHC potential Sensitivity to angle a ATLAS compensate large backgrounds with multi-channel fits.

Slide32: 

DGs and fs measured from Bs  J/yf, indep. measurement of fs from Bs  J/yh. DGs, Gs and fs are determined simultaneously with helicity amplitudes A||(t=0), AT(t=0), A0(t=0), d1, d2 from angular analyses of Bs  J/y (mm)f(KK). DGs can be determined with a relative error of 12% (stat) with 30 fb-1. fs depends on xs: for Bs  J/yf, sensitivity in the range 8-15% for xs=20-40 (SM range) Bs  J/yh, sensitivity for fs in the range 27-31% for xs=20-30 DGs and fs from B0sJ/yf (h)

DGs and fs from B0sJ/yf (h): 

DGs and fs from B0sJ/yf (h)

Background,Signal (new cuts): 

Background,Signal (new cuts) CMS vertex cuts gives rejection better than 2.310-4 Try to apply similar cuts for ATLAS data compare two vertex fit procedures – CTVMFT (CDF) and dedicated fit procedure from xKalman (private)

Discussion: 

Discussion xKalman vertex fit gives a better rejection than CTVMFT one The quantities used for cuts can correlate The plot shows the profile histogram of decay length L vs. error on this value  for the background events. For xKalman it is correlated – i.e. larger decay length has larger errors (as it should be for BG) This explain the better rejection of this algorithm – events survived L andgt; L_cut will be removed by cut andgt; _cut xKalman CTVMFT andlt;andgt; andlt;L/andgt;

B production at LHC (III): 

Bm Bd  J/yKs0 Bm Bs  J/yf ATLAS - proposal for measuring b-b production correlations using exclusive B-decays and semileptonic decays to muons No degradation of efficiency as b-b close in space. In Bs case – interesting specific background Km originating from s-quark associated with Bs production. Need Be Bs  J/yf Df=f J/y - fm B production at LHC (III)

Bd  K* g for 2 fb-1 with Initial Layout: 

Bd  K* g for 2 fb-1 with Initial Layout Level 1: m6 Level 2: g: cluster ET cut, shower shape cuts, g/p0 rejection K*: 2 charged (opposite-sign) tracks, pT cuts Event Filter: g: level-2 confirmation K*: vertexing, impact-parameter cuts 2.8% rec. efficiency, 57 MeV mass resolution Combinatorial background from bbm(6)X was considered. Background from B0K*p0 is under investigation.

Installation schedule: 

Installation schedule The schedule consists of 6 major phases which are partially overlapping + 50 days for global commissioning and 40 days for cosmic tests.