Studies of Beauty at H1 and ZEUS

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1 Studies of QCD and High Energy Hadronic Interactions March 12th 19th 2005 XXXXth Rencontres de Moriond I. Bloch, DESY Hamburg / Hamburg University Introduction & Theory Measurement methods & Results: gp m+jets DIS m+jet DIS inclusive F2bb Summary & Outlook 1

2 HERA: ep collisions within H1 & ZEUS (820 GeV) e 27.5 GeV p 920 GeV (820 GeV) ep centre of mass energy: : : 300 GeV 318 GeV H1&ZEUS integrated Luminosity: 9600 / e p scattering: L 100 / 40 pb1 e p scattering: L 15 / 20 pb1 2

3 Beauty Production in ep collisions Dominant process in ep collisions: BosonGluonFusion Multiple scales: mb ~ 5GeV ptb ~ typically few GeV Q2 2 < 1 GeV Photoproduction (gp) ~ >~ 1 GeV2 Deep inelastic scattering (DIS) NLO calculations with different schemes depend on dominant scale: massive schemeƒ FFNS: Q2, ptb2 mb2 massless schemeƒ ZMVFNS: Q2, ptb2 mb2 combined massive massless: VFNS 3

4 Beauty Production in ep collisions } Parton shower Prediction: Describes: LO+PS: PYTHIA, HERWIG (DGLAP) RAPGAP (DGLAP) CASCADE (CCFM) gp DIS gp&dis NLO: gp DIS FMNR HVQDIS 4

5 Measurement techniques m+jets Tag m+jets beauty events by exploiting: mmomentum relative to associated jet, ptrel large B mass ptrel Q2>2 GeV2 Jet m B ''long'' lifetime signed impact parameter relative to vertex/beamspot, d d B+ Jet 5

6 Beauty in gp, m+jets and d (1) hepex/ H1 Beauty in m+dijet: Simultaneous twodimensional ptrel and d fit. Method yields enhanced statistics and reduced systematic uncertainties. gp 9900: 50 pb1 Q2 < 1 GeV2 y [0.2, 0.8] ptm > 2.5 GeV hm [0.55, 1.1] ptjet > 7 (6) GeV h jet lab < 2.5 Shape of NLO (FMNR) follows hm data, though data tend to slightly higher values. 6

7 Beauty in gp, m+jets and d (2) gp 9900: 50 pb1 Q2 < 1 GeV2 y [0.2, 0.8] ptm > 2.5 GeV hm [0.55, 1.1] x obs = Jet E p z Jet E p z h E p z 1 2 LO: part of photon energy in hard scatter low high Data steeper in ptm,jet and slightly higher at low xgobs. 7

8 Beauty in gp, m+jets and d (3) comparison with ZEUS H1: ptrel + d, 9900 hepex/ ZEUS: ptrel, 9600 hepex/ Agreement within errors of H1 and ZEUS. 8

9 Beauty in DIS, m+jet and d (1) hepex/ Simultaneous fit to ptrel and d as shown before (Q2 < 1 GeV2), now for 2 GeV2 < Q2 < 100 GeV2 (DIS) using the breit frame for the jet: DIS 9900: 57 pb1 Q2 [1, 100] GeV2 y [0.1, 0.7] ptm > 2.5 GeV hm [0.75, 1.15] ptjet > 6 GeV hlabjet < 2.5 Q2 shape is described, though data slightly above the NLO (HVQDIS) prediction in DIS as in gp. 9

10 Beauty in DIS, m+jet and d (3) DIS 9900: 57 pb1 Q2 [1, 100] GeV2 y [0.1, 0.7] ptm > 2.5 GeV hm [0.75, 1.15] Data higher at low ptm as for the gp measurement. Higher data also in forward h. 10

11 Beauty in DIS, m+jet and d (3) comparison with ZEUS ZEUS Q2 [1, 1000] GeV2 y [0.05, 0.7] ptm > 2.0 GeV hm Kinematic ranges differ, but similar trend in h is seen. Not reproduced by the predictions. [1.6, 1.3] H1 Q2 [1, 100] GeV2 y [0.1, 0.7] ptm > 2.5 GeV hm [0.75, 1.15] hepex/

12 Beauty contribution to F2 in DIS method Measure bb contribution to proton structure F2 at Q2>150 GeV2. Method: inclusive lifetime tagging use all tracks (p > 0.5 GeV) with at least t one silicon track. S1(2) = significance S1(2) = d/sd of (second) largest imp. parameter d. ( d < 0.1cm) S1(2) sign from jets (97%) or hadronic final state, select only: sign(s1) = sign(s2) High statistics and high separation of beauty at high S2. Fitted to determine beauty fraction: 12

13 F2bb in DIS at high Q2 hepex/ Differential fraction of cross sections: 2 q q 2 d d f q q = 2 / 2 dq dx dq dx Beauty contribution to F2: Integrated cross sections, Q2 > 150 GeV2, 0.1 < y < 0.7: sbb = pb H1 PDF 2000massless[ZMVFNS] sbb= 52 pb NLOmassive massless[vfns] sbb= 47 pb NLOmassive[FFNS] sbb= 37 pb 13

14 Beauty in gp, m+jets or d, HERA II ZEUS: First look at impact parameter method: based on 20 pb1 (Vertex detector in ZEUS since upgrade 2001) m+dijet ptrel Methods and new detectors work heading for improved HERA II measurements. 14

15 Summary Jetm ptrel and impact parameter measurements have been performed in DIS and gp H1 and ZEUS measurements agree Beauty data in general agreement with NLO data generally slightly higher, localised m at low p (gp+dis) and T forward h (DIS) inclusive DIS impact parameter measurement used for F2bb is in good agreement with NLO 15

16 Outlook HERA II is running smoothly in electron mode already accumulated more e data than ever before new detectors performing well, quantitative results soon expect higher precision results. 16

17 p u k c a b s e il d s w ll o fo 17

18 Backup: Data NLO ratio This is just a rough comparison. Q2 is not the driving scale in the whole range! Main caveats: NLO has been extrapolated to hadron level using different approaches NLO has been calculated for different sets of scales and parameters, same for the uncertainty Cross section definitions and kinematic ranges somewhat different 18