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1 bb cross section: blessing CDF note 8589 Sofia Vallecorsa University of Geneva

2 Outline Jet Corrections Tagging efficiency bb-fraction Scale factor Unfolding factors Systematics bb cross section

3 «SVT» JET JetClu cone 0.4 SecVtx TIGHT tagged jet corrected E T >30 GeV, η <1.2 Matched to L3 jet with E T >20 GeV (δr<0.4) Matched to L2 cluster E T >15 GeV, η <1.5 (δr<0.4) Matched to SVT track, d0 >120 µm, p T >2GeV/c, η <1.2 (δr<0.4) Matched to Si track d0 >120 µm (δφ, δcurv) On JET20: only 0.1% events TWO «SVT» jets have HIGH_PT_BJET bit off Negligible effect compared to other systematics

4 bb cross section d" detd# = 2b N 2SVT $ f 2SVT %# $ %E T $L$& 2SVT $ SF jet1 $ SF jet 2 N 2SVT : Events with two «SVT -tag» jets: Leading jet: E T corr >35 η <1.2 Second jet: E T corr >32 η <1.2 (changed from pre-blessing!) f 2b 2SVT: bb-jets fraction Use Secondary vertex masses TFractionFitter standard routine Templates for Σ jet M jet (M jet : SecVtx Mass) ε 2svt : Efficiency for 2 SVT-jets Measured from PYTHIA bb SF jet1, SF jet2 : Official scale factor, (run a check first): SF = ± (stat) ± (syst) Standard vertex quality cuts

5 Jet Energy Corrections Need additional correction for b jets: Calculate average Et correction (relative to L5 generic corrections): Match CAL jets to HAD jets (ΔR<0.4) Fit correlation Et(CAL) vs Et(HAD) Check fit consistency R= (Et(HAD) - Et(CAL)corr) / Et(HAD) Calculate unfolding factor to correct Et smearing effect

6 Fit - SVT tagged jets Correction is of the order of 5%: Cut on the SVT-tag jet L5 E T >30 is raised to take it into account: (L5+ add.c.) E T >35 GeV, (L5+ add.c.) E T >32 GeV (second jet) R = Et HAD " Et CORR Et HAD

7 Tagging efficiency Efficiency for 2SVT-tag jets in event: Calculate directly «per event» efficiency Systematics: b-quark content of the jet

8 bb fraction Two SVT tagged jets Sum-up the SecVtx masses of the two jets: one entry per event Mass template: bb template Bkgd template (bc, cc, cl, ll, bl..) Fit fraction using TFractionFitter in different di-jet average Et bins E T bin (GeV) (32,40) (40,50) (50,60) (60,80) (80,100) ET> 100 ET> 32 B fraction 0.87 ± 0.04 % 0.88 ± 0.03 % 0.86 ± 0.04 % 0.78 ± 0.05 % 0.84 ± 0.06 % 0.75 ± 0.09 % 0.88 ± 0.04 %

9 bb fraction Systematics: Background composition (light vs charm) Track reconstruction ineff.

10 Unfolding Use dijet PYTHIA bb-hepg filtered sample ( pt>10, pt >18, pt>40, pt>60, pt>90, pt>120 GeV) - Apply L5 jet energy corrections + additional corr. - Build JetClu calorimeter/hadronic jets - Identify each as a b-jet (match to a B-hadron) - Only central jet ( η <1.2) Et>35 GeV,Et>32 GeV at the pre-blessing: Et>30, Et>30 GeV

11 Unfolding factors: Leading jet Et Invariant mass Δφ

12 Systematics Jet Corrections: Standard systematics Tagging: Efficiency: quark multiplicity in the jet Fraction: Quark multiplicity in the jet Background template composition Track reconstruction efficiency b-jets correlation in templates Unfolding: Et dependence

13 Total Jet Corr. systematics Use Jet Energy E T bin (GeV) (+1 σ) (-1 σ) group standard routine Add systematics from specific corrections (35,41) (41,47) (47,54) (54,61) 19% 20% 17% 15% 17% 15% 14% 13% (61,69) 13% 11% (69,78) 18% 13% (78,88) 11% 10% (88,99) 18% 18% (99,110) 10% 15% (110,140) 18% 7% (140,180) 14% 14% (180,230) 17% 20%

14 Total Jet Corr. systematics (2) Invariant Mass & Δφ Mass Δφ

15 Unfolding Compare Et spectrum in data and MC. Ratio Data/MC after unfolding data cross section Fit ratio to third order polinomial Reweight MC Calculate new unfolding Take the difference as a syst. err.

16 Unfolding

17 Total systematics E T bin (GeV) Add all uncertainties in quadrature 6% from lumi is not included (35,41) (41,47) (47,54) (54,61) (61,69) 25% 26% 23% 23% 21% -23% -24% -23% -22% -19% (69,78) 24% -19% (78,88) 20% -18% (88,99) 24% -21% (99,110) 19% -16% (110,140) 25% -21% (140,180) 23% -19% (180,23) 24% -21%

18 NLO prediction Use + Herwig v Jimmy v4.3 bb events with: CTEQ6m PDFs, µ R = µ F = sqrt(p 2 +m 2 ) Pt (bquark) > 10 GeV/c (before pt >22 GeV/c) η <1.75 Full simulation 6.1.4mc (redecay using EvtGen) Stntuple dev243 Hadron level jet cross sections

19 Unfolded Cross section - Leading jet E T

20 Unfolded Cross section - Invariant Mass

21 Unfolded Cross section - Δφ

22 Summary Questions and remarks: Changed Et cut Unfolding systematics generation cut Total cross section Data Pythia Herwig CDF Run II Preliminary σ(bb) [pb] η 1,2 <1.2, E T,1 >35 GeV, E T,2 >32 GeV 2360 ± 70 (stat) ± 133 (syst) 2140 ± 22 (stat) 2201 ± 29 (stat) 2259 ± 44 (stat)

23 More..

24 Cross section - linear scale

25 Reweighted MC samples PYTHIA bb Pt > 10 Pt > 18 Pt > 40 Pt > 60 Pt > 90 Pt > 120 σ (µb) (nb) 3.97(nb) p ˆ t HAD jet Et Scale each pthat bin for relative luminosity Normalize to highest pt sample luminosity CAL jet Et

26 Tagging efficiency Found a correlation between SVT tagged jets Select events with: >2 jets E T >30 GeV, η <1.2 >2 good SVT tracks Order jets (E T,φ,η.. etc..) Count: 1. First jet is SVT-tagged -> Look at the second jet (RED) 2. First jet is NOT SVT-tagged -> Look at the second jet (BLACK) SVT tag simple tag -->DIFFERENCE! NOT the same problem for «simple tag»

27 Tagging efficiency Main difference: matching to the track Select «good» tracks ( d 0 >120µm,pt>2 GeV/c) Track-Track and Jet-Track show the SVT tracks are «grouped» ΔR(jet-track) ΔR(track-track)

28 bb fraction - fit 32<E T <40 GeV 40<E T <50 GeV 50<E T <60 GeV 60<E T <80 GeV 80<E T <100 GeV E T >100 GeV

29 Scale Factor Use muon jets ( jet Et - up to GeV) MC: btop7a, btop8a Herwig dijet + HEPG filter e>8 GeV, µ pt> 9 GeV Run TrigSim. with correct beamline good run list - but exclude some run (beamline) Data: inclusive µ sample (bmcl0d,bmcl0h) goodrun list CMU+CMP+Si+SVT Measure efficiency for «SVT - TAG» jets (JetClu tight SecVtx - SVT track (d0>120 µm)

30 Scale factor Select «good muon»: Pt > 9 GeV/c CMU stub dx <3cm, CMP dx <5cm Track z0 <60cm, z0 -Zvtx <5cm Iso(cone 0.4) > 0.1 Require track to hit all SVX layers Match good muon to jet (taggable, Et>20, η <1.2) Correct jet Et, and P E corr = E L5 E raw "2gev E raw + p t,µ r P corr = r P + r p µ # 1" 2gev & % $ p ( µ ' Select only highest Pt muon Search for away jet (Et>20, η <2, Δφ >2rad, mass>1.5)

31 Scale factor: single tag Reconstruct muon pt relative to corrected jet axis Fit b fraction in muon jet before and after tagging Two componets FIT: b jets and c templates from µ sample (btop7a, btop8a) (or light jet templates from dijet pythia (jqcd1f, jqcd2f)) " = N e away # N away f after f before

Scale factor MC: N (µ+,away+) = 1795 N (away+) = 7952 ε = 0.225 +/- 0.007 DATA: N (µ+,away+) = 1191 N (away+) = 7485 ε = 0.22 +/- 0.

32 Scale factor MC: N (µ+,away+) = 1795 N (away+) = 7952 ε = / DATA: N (µ+,away+) = 1191 N (away+) = 7485 ε = / SF = / Use official value: ± ± (tight SecVtx + SVT track) (1.066 ± 0.045) - ( ± )* E T

33 bb fraction - templates To have enough statistics in the templates Combine couple of jets coming from different events. CHECK: 2 jets in different events vs 2 jets in the same event 32<E T <40 GeV 40<E T <50 GeV 50<E T <60 GeV 60<E T <80 GeV 80<E T <100 GeV E T >100 GeV Effect is small + Kolmogorov test

34 Templates: cc content Double cc content Half cc content Et bin (GeV) b fraction Et bin (GeV) b fraction 32<Et< ± <Et< ± <Et< ± <Et< ± <Et< ± <Et< ± <Et< ± <Et< ± <Et< ± <Et< ± 0.07 Et> ± 0.09 Et> ± 0.09 Et> ± 0.04 Et> ± 0.04

35 b multiplicity in the jet Eff. is different according to b content in the jet In 2SVT-tagged jets events select couples with: One jet including 2b quarks Two jets including 2b quarks < 3% < 1.5 %

$Quark multiplicity: b fraction (mass templates): Double fraction of bb jets events in mass templates and fit:: (same check on jet including >1c quark) 32<E T <40 GeV 40<E T <50 GeV 50<E T <60 GeV$

36 Quark multiplicity: b fraction (mass templates): Double fraction of bb jets events in mass templates and fit:: (same check on jet including >1c quark) 32<E T <40 GeV 40<E T <50 GeV 50<E T <60 GeV 60<E T <80 GeV 80<E T <100 GeV E T >100 GeV E T bin (GeV) (32,40) (40,50) (50,60) (60,80) (80,100) Et>100 Et>30 b fraction 0.87 ± 0.04 (0.87) 0.88 ± 0.03 (0.88) 0.86 ± 0.05 (0.86) 0.78 ± 0.07 (0.78) 0.83 ± 0.07 (0.84) 0.79 ± 0.09 (0.75) 0.86 ± 0.04 (0.88)

37 Templates composition Light jets contribution to mass templates For light jet to c jet proportion rely on Pythia -> change light jet fraction E T bin (GeV) (35,41) (41,47) (47,54) (54,61) (61,69) (69,78) (78,88) (88,99) (99,110) (110,140) (140,180 (180,230) Syst.err. 0.5% 0.5% 0.5% 0.7% 0.5% 0.5% 1% 1% 2% 2% 2% 2%

38 Other systematics for b fraction Track reconstruction efficiency (CDF 6894) -> 3% shift in mass template E T bin (GeV) (35,41) (41,47) (47,54) (54,61) (61,69) (69,78) (78,88) (88,99) (99,110) (110,140) (140,180 (180,230) Syst.err. 5% 5% 5% 6% 6% 7% 8% 8% 8% 8% 7% 7%

Feasibility of a cross-section measurement for J/ψ->ee with the ATLAS detector

Feasibility of a cross-section measurement for J/ψ->ee with the ATLAS detector ATLAS Geneva physics meeting Andrée Robichaud-Véronneau Outline Motivation Theoretical background for J/ψ hadroproduction