QCD and High Energy Hadronic Interactions. Northwestern University. Heidi Schellman. Experimental Summary. 40 th Rencontres de Moriond

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1 Experimental Summary 40 th Rencontres de Moriond QCD and High Energy Hadronic Interactions Heidi Schellman Northwestern University

2 Thank you To the conference organizers The secretariat The Hotel Planibel The participants, especially those who fed me background information Apologies to Those who sent me information which still didn t make into this talk

3 QCD Interesting on its own Perturbative evolution bound states new states Engineering requirement for most other physics weak angles hadron scattering rates heavy ion physics new physics searches

4 Outline Alternate between QCD for purists and applications Spectroscopy Structure Functions Fragmentation and initial state Heavy Ions LHC Prospects

5 First some pure QCD fun Spectroscopy Many states have been floating in limbo for decades We know a lot about states directly accessible from the photon but others quantum states are much harder to produce. KLOE, BES, Cleo, Babar, Belle (and sometimes high energy colliders) now are QCD spectroscopes. Can produce exclusive final states, determine quantum numbers from initial particle and other known particles in the decay chain. σ,κ,a 0,f 0 s,d sj,h c,x(3872),y(3970).. Structure functions

6 B-> Khh Dalitz Analysis from Babar

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8 A digression into Applied QCD - Babar Dalitz Analysis One output of this analysis can be CP violation.

9 Previously rare resonances κ, σ, f0

10 Information about couplings from KLOE

11 X(3872) was at Moriond last year but not well understood.

12 Swanson D*D molecule model predicts equal BF to ρ and ω ω

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14 h c ( 1 P 1 )at Cleo C

15 ?? Isospin violation in ψ K*K

16 Prospects Babar, Belle, Cleo-c, BES, and KLOE already have more data to analyze and will continue running. We can expect substantial increases in our understanding of many states which were not possible to study in the past. More to study Baryon Threshold enhancements observed at Cleo-C in J/ψ, Belle and Babar in B decay.

17 QCD fits to jets and Structure Functions H1 and Zeus G/G

18 New structure function fits from H1 and Zeus, use CC event to pin down q/qbar differences, use jets to pin down gluons. Only use data from HERA

19 Effect of adding the jets information on the fits.

20 Hera PDF s

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22 G/G from photon-gluon fusion->high pt hadrons We also saw preliminary results from Phenix-spin

23 Back to engineering Use of b sγ as speedometer Fragmentation Models/initial state radiation

24 b sγ as quark radar The photon energy spread due to recoil should directly reflect the motion of the b quark. Can use b-sγ to test models of b quark motion, then use those to improve understanding of b d transitions

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26 Fragmentation functions from Hermes Diffractive contributions to fragmentation functions derived from DIS data are important at low t, coherent component of σ A scales with A 2 Fraction from Diffractions <Q 2 > ~ 2.5 GeV 2

27 Note from Heavy Ion Introduction E. Wang & XNW 2000 de dx 2 2 Cα s GeV 0.5 GeV/fm in Au nuclei

28 Charm fragmentation at HERA

29 Status of Parton Hadron translation New data working its way into use LEP fragmentation CDF Tune A Generally consistent across processes ee, ep, pp Some examples

30 Study dijet angle, compare NLO calculation with LO+ HERWIG/Pythia. Note φ < 2/3π does not exist in pure LO!

31 B Production at the Tevatron Finally NLO QCD and data agree PDF s add more gluons Fragmentation measurements from LEP define your signal b- quark, B +, H b All this can shift the same matrix element prediction by factor more than 2!

32 HERA Zeus/H1 Can t be completely complacent yet, Zeus/H1 see discrepancy at high η

33 Test of QCD/Fragmentation Use models tuned at LEP on Jade Data LEP tunes appear to work very well for other e + e - experiments.

34 Now use that engineering for some weak interaction physics at the Tevatron B s mixing Higgs searches

35 Back to pure QCD fun - Heavy Ion Physics Model independent discussion New regime, new data, lots of information

36 R Heavy Ion Observables AB = N σ binary AB AB σ NN Reaction plane (Ψ R ) z z dn ch N0 v1 φ v2 φ ϕ = + + +L d (1 cos 2 cos 2 ) pp vs A d vs AA see initial vs final state effects Central vs Peripheral High vs low Rapidity Heavy vs light Open vs closed Charm High vs low sqrt(s) y x (defines Ψ R )

37 centrality and sqrt(s) dependence PERIPHERAL CENTRAL 62.4 GeV 200 GeV PRL 94, (2005)

38 Pion suppression, Proton not so suppressed. R AB = N σ binary AB AB σ NN

39 Energy dependence of particle fractions

40 Open Charm suppression at high p t Total production not suppressed R AA = T AA dn d AA σ pp PHENIX Preliminary

41 J/ψ/ψ suppression

42 Centrality dependence of ω/φ

43 More observables Azimuthal (de)correlation 2-point correlation functions at low pt

44 Azimuthal correlation for wide rapidity separation Pedestal&flow subtracted

45 C Short range correlations r ( q r, k ) = 1 + λ ( v k ) e q 2 out R 2 out q 2 side R 2 side q 2 long R 2 long Q T Q R R R 2 o 2 s 2 l r ( ) ( ~ 2 K = x~ out β t ) ( K ) r 2 r ( K ) = x~ side ( K ) r ( K ) ( x~ ~ 2 r = β t ) ( K ) long l r p 1 p 2 Q L Q T Q O Q S p 1 p 2 beam direction beam direction

46 R long ~R out???

47 You re on new turf Most HEP experiments are 4 th generation and have to work hard to do better than the previous 3 generations. You are in a completely new regime. Have some fun!

48 Back to the HEP frontier Top at the Tevatron Top at the LHC Strategies for the future

49 Top at the Tevatron Single top limits We have 2-3 times more data already. Most systematic errors scale with statistics at this point

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51 Top at the LHC. Other top in event decays semileptonically. Can use the W jj to calibrate hadronic energy scale Can also use it to make Higgses

52 Strategies for the LHC We (finally, probably) understand fragmentation, initial state QCD effects and PDF s well enough to model most processes at hadron colliders. How will we go about looking for new physics model independent/dependent cut optimization?

53 The values of the 105 MSSM parameters are: 1 M 2 M 3 M µ = y e = y d = y u = a e = a d = a u = e m~ = d m~ = u m~ = L m~ = Q m ~ 2 m Hu 2 H d m b

54 Knuteson et al. Example of a model independent scan

55 Model Specific MSSM Scans from LEP

56 Example of a LEP scan for the M h -max scheme

57 Cut scan for specific msugra models Do a scan in 7 cut variables to find the most significant signal/background in 20 chosen regions of MSugra space m 0 0 m 1/

58 What about the observables we don t normally think of?

59 Considerations Broad searches give broad answers Specific searches give specific answers Theory can motivate new techniques But it can also confine you in parameter space

60 Check of tag/calibration in Z 0 bb CDF Run 2 preliminary - L=333 pb Selected events Background Z signal: 3394 ± 515 events Fit result CDF PRELIMINARY 100 Observed events 80 Predicted bgr Dijet Mass (GeV/c 2 ) Events per 10 GeV/c 2 Events per 10 GeV/c 2 Events per 5 GeV Run I 0-10 Excess over background Expected MC shape (PYTHIA) Dijet Invariant Mass (GeV/c 2 ) Dijet invariant mass (GeV) ~10,000 Z µµ in same acceptance*luminosity

61 Current status