Implications of HERA measurements for LHC

Transcription

1 Imlications of HERA measurements for LHC M. Diehl Deutsches Elektronen-Synchroton DESY 3 August 7 DESY

2 . Structure functions and arton densities. Diffraction 3. Summary (with aologies) will not cover many detailed studies of final state: jets, charm and bottom roduction, multile interactions,... detailed recent overview 3rd HERA/LHC Worksho, March 7 htt://indico.cern.ch/conferencedislay.y?confid=784 Thanks to: H. Abramowicz, J. Bartels, O. Behnke, L. Dixon, C. Gwenlan, H. Jung, M. Klein, G. Kramer, S. Moch, L. Motyka M. Diehl Imlications of HERA measurements for LHC

3 HERA F -log (x) em F x=6.3e-5 x=. x=.6 x=.53 x=.4 x=.5 x=.63 x=.8 x=.3 x=. x=.3 x=.5 x=.8 x=.3 ZEUS NLO QCD fit H PDF fit x=. H 94- H (rel.) 99/ ZEUS 96/97 BCDMS E665 NMC x=.3 x=.5 x= H+ZEUS, Moriond 4 x=.3 x=.8 x=.5 x=.4 x=.65 Q (GeV ) chief discovery of HERA: stee rise of roton structure function insight into QCD dynamics many theory develoments fits of arton densities (PDFs) arton LHC asects: recision hysics of small-x gluons and sea M. Diehl Imlications of HERA measurements for LHC 3

4 Imact of PDF uncertainties on LHC examle rocesses Higgs roduction W ±, Z roduction ossible luminosity monitors most PDFs now with errors reflect error roagation fitted data PDF arameters not uncertainties from theory, arameterization, data selection,... M. Diehl Imlications of HERA measurements for LHC 4

5 Imact of PDF uncertainties on LHC examle rocesses Higgs roduction W ±, Z roduction ossible luminosity monitors most PDFs now with errors reflect error roagation fitted data PDF arameters not uncertainties from theory, arameterization, data selection,... σ [nb] σ(w + ) Br(lν) σ(w ) Br(lν) 3 σ(z) Br(l + l ) 5 ZEUS-JETS ZEUS-S CTEQ6. CTEQ6.5 MRST MRST4 numbers from A. Cooer-Sarkar [he-h] M. Diehl Imlications of HERA measurements for LHC 5

6 Higgs roduction comare MRST, CTEQ6, Alekhin σ(gg H) [b] s = 4 TeV MRST CTEQ Alekhin.7.5..σ(qq Hqq) [b] s = 4 TeV.9.8 MRST CTEQ Alekhin M H [GeV]..3.5 MRST. CTEQ.5 Alekhin. σ(gg H) [b].95.9 s =.96 TeV. 4 6 M H H [GeV] 8. MRS CTE Alekh σ( s A. Djouadi, S. Ferrag, he-h/39 M. Diehl Imlications of HERA measurements for LHC 6

7 MRST6 vs. Alekhin MRST6 vs. Alekhin 6 xg(x,q =5GeV ) 8 Alekhin NNLO 6 4 NNLO x - MSTW, [he-h] Q = ( GeV) M. Diehl Imlications of HERA measurements for LHC 7

8 Main constraints on low-x gluon density scaling violations in F (x, Q ) cross talk gluons sea quarks M. Diehl Imlications of HERA measurements for LHC 8

9 Main constraints on low-x gluon density inclusive charm roduction: F c c significant changes in theory used by global arton analyses Different schemes: FFNS (fixed flavor number) : n f = 3 PDFs for light q and q c, c only from fixed-order hard scattering misses αs n log m (m c/q ) terms from higher orders found to work for HERA F c c u to rather high Q ZM-VFNS (zero-mass variable flavor number) : change from n f = 3 to n f = 4 quark PDFs at µ = m c quarks treated as massless in hard scattering resums α n s log m (m c/q ) terms via DGLAP evolution adequate for Q m c but not for Q few m c c quark PDFs needed for high-t charm roduction at HERA, Tevatron and LHC M. Diehl Imlications of HERA measurements for LHC 9

10 Main constraints on low-x gluon density inclusive charm roduction: F c c significant changes in theory used by global arton analyses Different schemes: FFNS (fixed flavor number) : ZM-VFNS (zero-mass variable flavor number) : GM-VFNS (general mass variable flavor number) : interolate between FFNS at low and ZM-VFNS at high Q F c c at HERA and b rod n at LHC technical choices in matching n f and n f + descritions m c in kinematical variables, in hard-scattering coefficients at NNLO discontinuities in both PDFs and coefficient fcts. but not in observables R. Thorne, 6 analogous discussion for bottom b quark PDFs needed for LHC M. Diehl Imlications of HERA measurements for LHC

11 F cc _ / CTEQ5F3 3 Q = GeV CTEQ5F3 CTEQ6.5 Q = 4 GeV MRST4FF3 MRST4 MRST NNLO Q = 7 GeV 3 3 Q = GeV ZEUS D H D H Dislaced Track Q = 6 GeV Q = 8 GeV Q = 3 GeV Q = 3 GeV Q = 5 GeV exerimental errors may decrease by factor with full HERA data O. Behnke HERA/LHC Worksho 7 constraints on theory/pdf fits P. Thomson, he-h/733 x M. Diehl Imlications of HERA measurements for LHC

12 Some recent PDF fits MSTW [he-h] global fit, NNLO for DIS and Drell-Yan refined treatment of c, b in GM-VFNS at NNLO significant changes w.r.t. MRST 4 NNLO CTEQ6.5 he-h/768, he-h/7, he-h/654 global fit, NLO, GM-VFNS revious CTEQ6. had ZM-VFNS significant changes Alekhin 6 S. Alekhin, K. Melnikov, F. Petriello, he-h/6637 DIS and DY data at NNLO with n f = 3 FFNS charm and bottom contrib. to F at O(αs) BBG J. Blümlein, H. Böttcher, A. Guffanti, he-h/67 non-singlet PDFs (no gluon) from F F n at NNLO and N 3 LO Fits also ermit recise determination of α s cometitive with e + e M. Diehl Imlications of HERA measurements for LHC

13 effect of CTEQ6. CTEQ6.5 on LHC cross sections Imact of CTEQ6.5M,S,C PDF s on σ tot s at LHC + W.-K. Tung, HERA/LHC worksho, 3/7 M. Diehl Imlications of HERA measurements for LHC 3

14 Structure functions and arton densities Diffraction Summary H (rel.) ZEUS (rel.).8.8 xf 3 γz xf 3 γz Q searation =5 GeV Q of quark flavors =5 GeV and of q vs q crucial non-hera inut:.4 d vs ū: Drell-Yan, CDF W ± asymmetry (see ABS S-4). s and s: ν and ν DIS: CDHSW, CCFR, CHORUS, NuTeV HERA large Q data... statistics crucial - - x xf 3 γz x H+ZEUS Combined (rel.) Q =5 GeV H PDF ZEUS-JETS PDF - - x H+ZEUS, ICHEP6 artial HERA II stat. e struct. fcts.: recise theory NC beam charge asy. F γz 3 q q at small x NC beam ol. asy. F γz u + d at large x CC: e + u + c and d + s e d + s and ū + c s, s from charm tagging? M. Diehl Imlications of HERA measurements for LHC 4

15 imroved PDFs at medium x jet roduction at LHC and heavy new articles... simle estimate of HERA II imact only statistical errors assumed 7 b, have 57 b fit only to HERA data (nb/gev) dσ/de T Fractional Uncertainty < η Jet < < η Jet < < η Jet < NLO QCD (JETRAD) PDF: ZEUS-JETS PDF: HERA-II PROJECTION Jet + X s = 4 TeV JETCLU Cone R= (GeV) Inclusive Jet E T C. Gwenlan et al., he-h/59 M. Diehl Imlications of HERA measurements for LHC 5

16 Gluon LO, NLO and NNLO 5 Q = GeV Q =5 GeV NLO fit NNLO fit 5 LO fit Back to small x xg(x,q ) 5 radiative corrections are imortant at low x see changes of g(x) extracted at LO, NLO, NNLO 3 Q = GeV 5 4 Q = GeV NB: g(x) is not an observable but wait a few slides... xg(x,q ) x x R. Thorne, HERA/LHC worksho, 3/7 M. Diehl Imlications of HERA measurements for LHC 6

17 Small-x resummation G. Altarelli, R. Ball, S. Forte (ABF); C. White and R. Thorne; M. Ciafaloni, D. Colferai, G. Salam, A. Stasto (CCSS) at small x large logarithms α n s log m x in fixed-order evolution kernels and hard-scattering coefficients resum in BFKL aroach at NLL, i.e. α s (α s log x) n roject out leading twist art join on to fixed-order results at higher x technical issues: running of α s choice of scheme recent rogress: inclusion of quarks M. Diehl Imlications of HERA measurements for LHC 7

18 first alication in global PDF fit: C. White and R. Thorne, he-h/64 resummed evolution kernel at NNL, coefficient fct. imroved LL xg(x) Q =GeV NLL+ NLL()+ NLO+ - Q =GeV x x C. White, R. Thorne, [he-h] M. Diehl Imlications of HERA measurements for LHC 8

19 The longitudinal structure function F L is a basic observable together with F describes inclusive cross section starts at order α s directly sensitive to g(x) discriminates between theoretical aroaches F L (x,q ) F L (x,q ) Q = GeV NLL+ LO NLO NNLO Q = GeV Q =5 GeV Q = GeV x x C. White, R. Thorne, [he-h] M. Diehl Imlications of HERA measurements for LHC 9

20 HERA low- and medium-energy runs An intermediate energy 9 GeV 3 b GeV 7 b - 46 GeV b - ) (GeV Q ZEUS First Events from HERA Runs at s = 5 GeV 3 = 7 θ e = 5 GeV E e ) (GeV Q y ZEUS First Events from HERA Runs at s = 5 GeV 3 Max Klein low energy run DIS7 rojected errors for low-energy data M. Klein, DIS, March 7 = 7 θ e y = 5 GeV E e M. Diehl Imlications of HERA measurements for LHC

21 Non-linear dynamics /Q transverse size of arton as seen by hard robe linear evolution: gluons slit high density at low x very high density: gluons recombine density saturates non-linear effects become strong at saturation scale Q s (x) non-linear evolution equations various degrees of aroximation Balitsky-Kovchegov, JIMWLK, omeron loos,... intense theoretical activity M. Diehl Imlications of HERA measurements for LHC

22 descrition of DIS rocesses in color diole icture diole scattering amlitude N q q γ M. Diehl Imlications of HERA measurements for LHC

23 descrition of DIS rocesses in color diole icture diole scattering amlitude N q q in non-saturated regime connect with leading-twist descrition N q q g(x) arameterizations of N q q incororating saturation attemts to derive/motivate from non-linear evolution eqs. Golec-Biernat, Wüsthoff; Itakura, Iancu, Munier; Marquet, Peschanski, Soyez; Kowalski, Motyka, Watt; Forshaw, Sandaen, Shaw;... successful fits to HERA F down to low Q and of F c c geometric scaling: F (x, Q ) only function of Q /Q s(x) γ with same N q q describe HERA diffraction next section no roof of saturation at HERA, but strong indications M. Diehl Imlications of HERA measurements for LHC 3

24 Where does saturation become imortant? recent estimates of Q s(x) in GeV x = 4 x = 6 Ref..7.9 G. Soyez, [he-h].8 4. H. Kowalski, L. Motyka, G. Watt, he-h/ K. Golec-Biernat, S. Saeta, he-h/6776 at HERA tyical Q s(x) < GeV HERA data have driven efforts to validate and quantify saturation imact on heavy-ion collisions RHIC, ALICE theory of color glass condensate rosects to study saturation in at LHC forward detectors M. Diehl Imlications of HERA measurements for LHC 4

25 >J $3 4 > ".#M: /(3 #!_M*:/(3 4 6 %* > *6!=+ # #*( *33 SL)+ J %&'6 '+ 88:88( #:b 4,3 "%*.$!"!#$%!"&'()#*+ 7,- M. Diehl Imlications of HERA measurements for LHC 5

26 F L once more exect bigger saturation effects than in F J. Bartels, K. Golec-Biernat, K. Peters, he-h/34 study in saturation model: ratio of full result and twist-two art: at Q = 5 GeV and x =.5 4 F full F t=.94 F full L F t= L.66 caveat: uses old model arameters, no udate of study but: trend follows from general considerations M. Diehl Imlications of HERA measurements for LHC 6

27 Diffraction in DIS have large fraction of events with leading roton/large raidity ga: γ X + overall fraction in DIS % M. Diehl Imlications of HERA measurements for LHC 7

28 3 i * x IP σ r D(3) / σ r x IP =.3 x=5e-5 β=.7 (i=8) x=8e-5 β=.7 (i=7) H Data Fit (a R + b R ln Q ) σ diff /σ tot flat in Q leading twist henomenon - - x=.3 β=.43 (i=6) x=. β=.67 (i=5) x=.3 β=. (i=4) x=.5 β=.7 (i=3) x=.8 β=.7 (i=) x=.3 β=.43 (i=) x=. β=.67 (i=) 3 H, he-ex664 Q [GeV ] twist-two descrit. of inclusive F ok for large Q factorization theorems but twist-two hard scattering arton showers hadronization models can miss imortant asects of final state M. Diehl Imlications of HERA measurements for LHC 8

29 H Data α IP = α IP incl / α IP = α IP incl ( - β). x IP σ r D(3) / σ r.5 β =. β =. β =.4 β =.65 β =.9 (x 5) Q [GeV ] σ diff and σ tot have very similar energy de ce in full Q range H, he-ex x M. Diehl Imlications of HERA measurements for LHC 9

30 naturally exlained in diole models with saturation caveat: in restricted kinematics models without saturation work as well J. Forshaw et al., he-h/686 kinematic reach imortant σ diff /σ tot ZEUS 994 Q = 8 GeV Q = 7 GeV Q = 4 GeV Q = 6 GeV M X < 3 GeV 3 < M X < 7.5 GeV σ diff γ < M X < 5 GeV. γ σ tot Im W(GeV) K. Golec-Biernat, M. Wüsthoff he-h/ M. Diehl Imlications of HERA measurements for LHC 3

31 Vector mesons and virtual Comton scattering for large Q or with heavy quarks σ rises much faster than σ tot also well described in saturation models γ γ (nb) σ γ* γ Q = 8 GeV H ZEUS (nb) σ W (GeV) Q (GeV ).5 γ* J/ψ H ZEUS H. Kowalski, L. Motyka, G. Watt, he-h/667 Boosted Gaussian Ψ V Gaus-LC Ψ V 3 W (GeV) M. Diehl Imlications of HERA measurements for LHC 3

32 Vector mesons and virtual Comton scattering for large Q or with heavy quarks σ rises much faster than σ tot also well described in saturation models γ γ (nb) σ γ* γ Q = 8 GeV H ZEUS in non-saturated regime have again leading twist factorization theorems generalized gluon distribution t t deendence satial distribution of gluons in lane to hadron momentum H. Kowalski, L. Motyka, G. Watt, he-h/667 (nb) σ W (GeV) Q (GeV ) γ* J/ψ H ZEUS Boosted Gaussian Ψ V Gaus-LC Ψ V 3 W (GeV) M. Diehl Imlications of HERA measurements for LHC 3

33 Raidity gas in hard or collisions at Tevatron order of magnitude more rare than in DIS Diffractive fractions for forward and central ga rocesses at CDF Hard rocess s (GeV) R = DIFF (%) Kinematic region TOTAL W ( eν)+g 8.5 ±.55 ET e, /E T > GeV Jet+Jet+G 8.75 ±. E jet T > GeV, η jet >.8 b( e + X)+G 8.6 ±.5 η e <., e T > 9.5 GeV J/ψ( µµ)+g 8.45 ±.5 η µ <.6, µ T > GeV Jet-G-Jet 8.3 ±.6 E jet T > GeV, η jet >.8 Jet-G-Jet 63.7 ±.9 E jet T > 8 GeV, η jet >.8 G= ga in raidity Table from: K. Goulianos, he-h/4735 M. Diehl Imlications of HERA measurements for LHC 33

34 gas in hard roc s: strong suression w.r.t. calculation using diffractive PDFs from HERA A. Rostovtsev ef D JJ σ( dijet + X + ) F D JJ (β) H fit- H fit-3 ( Q = 75 GeV ) CDF data E Jet, T > 7 GeV.35 < ξ <.95 t <. GeV. H 6 DPDF Fit A H 6 DPDF Fit B. β P. Newman and F.-P. Schilling HERA/LHC worksho, March 7 M. Diehl Imlications of HERA measurements for LHC 34

35 gas in hard roc s: strong suression w.r.t. calculation using diffractive PDFs from HERA A. Rostovtsev diffractive factorization in broken by sectator interactions ef D JJ σ( dijet + X + ) F D JJ (β) H fit- H fit-3 ( Q = 75 GeV ) CDF data E Jet, T > 7 GeV.35 < ξ <.95 t <. GeV. H 6 DPDF Fit A H 6 DPDF Fit B. β P. Newman and F.-P. Schilling HERA/LHC worksho, March 7 M. Diehl Imlications of HERA measurements for LHC 35

36 gas in hard roc s: strong suression w.r.t. calculation using diffractive PDFs from HERA A. Rostovtsev diffractive factorization in broken by sectator interactions ef D JJ σ( dijet + X + ) F D JJ (β) H fit- H fit-3 ( Q = 75 GeV ) CDF data E Jet, T > 7 GeV.35 < ξ <.95 t <. GeV. H 6 DPDF Fit A H 6 DPDF Fit B. β P. Newman and F.-P. Schilling HERA/LHC worksho, March 7 same interactions can oulate final state hysics of underlying event and multile interactions M. Diehl Imlications of HERA measurements for LHC 36

37 gas in hard roc s: strong suression w.r.t. calculation using diffractive PDFs from HERA A. Rostovtsev diffractive factorization in broken by sectator interactions ef D JJ σ( dijet + X + ) F D JJ (β) H fit- H fit-3 ( Q = 75 GeV ) CDF data E Jet, T > 7 GeV.35 < ξ <.95 t <. GeV. H 6 DPDF Fit A H 6 DPDF Fit B. β P. Newman and F.-P. Schilling HERA/LHC worksho, March 7 sect. interactions at least artly soft models HERA + Tevatron validate models extraolate to LHC M. Diehl Imlications of HERA measurements for LHC 37

38 Exclusive roduction at LHC roduce Higgs (or other articles) in clean environment need forward detectors Totem, FP, FP4 ext l challenge: triggers, low rates Why interesting? tagged rotons recise mass/width meas t selects CP = ++ states good signal/background ratio How to calculate? f f x,k T to 3 GeV (CP = + strongly suressed) HERA vector meson rod n generalized gluon distribution hard QCD corrections Sudakov suression factor H M. Diehl Imlications of HERA measurements for LHC 38

39 Exclusive roduction at LHC roduce Higgs (or other articles) in clean environment need forward detectors Totem, FP, FP4 ext l challenge: triggers, low rates Why interesting? tagged rotons recise mass/width meas t selects CP = ++ states good signal/background ratio How to calculate? H to 3 GeV (CP = + strongly suressed) HERA vector meson rod n generalized gluon distribution rescattering corrections: models checked against Tevatron ongoing CDF studies: + dijet +, + γγ + M. Diehl Imlications of HERA measurements for LHC 39

40 light SM Higgs W + W (one W off shell) very low background B. Cox et al., he-h/554 Excl. DPE H->WW: Event yield for L=3 fb- ExhuMe.3 and new RP accetances fully-let semi-let Mh[GeV] XBR[fb] Acc.[%] cms atlas cms atlas Total M. Taševski, HERA/LHC worksho, 3/6 8 M. Diehl Imlications of HERA measurements for LHC 4

41 light Higgs b b very low rate in SM with triggers and cuts must remove gg b b background (although is much lower than in inclusive case) detailed background calculations V. Khoze, M. Ryskin, J. Stirling, 6 M. Diehl Imlications of HERA measurements for LHC 4

42 light Higgs b b strongly enhanced rate in MSSM scenarios with high tan β Stat.sig=5 for H bb, mhmax sc., =-5 GeV tan β = 3 GeV M H = 5 GeV M H - L = 6 fb = GeV M H - L = 3 fb m A [GeV] - L = 6 fb M. Taševski, HERA/LHC worksho, 3/7 = 3 GeV M H = 35 GeV M H 6 M. Diehl Imlications of HERA measurements for LHC 4

43 Summary HERA has ioneered study of DIS at small x and at large Q recision PDFs theory of low x dynamics high fixed orders, resummation, non-linear dynamics diffraction: subtle QCD dynamics in final state HERA Tevatron exclusive roduction at LHC in some >SM scenarios could become discovery channel imortant results still to come from HERA II data statistics and kinematic reach longitudinal structure function F L M. Diehl Imlications of HERA measurements for LHC 43