1 / 38

Developments on cross-section and BR of Higgs production: part 2 BSM

Higgs Hunting Workshop, 30/07/2011. Developments on cross-section and BR of Higgs production: part 2 BSM. Mónica L. Vázquez Acosta - Imperial College (on behalf of the LHC Higgs Cross Section WG). Thanks to M. Flechl, R. Harlander, M. Krämer, M. Spira, M. Schumacher,

verne
Download Presentation

Developments on cross-section and BR of Higgs production: part 2 BSM

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Higgs Hunting Workshop, 30/07/2011 Developments on cross-section and BR of Higgs production: part 2 BSM Mónica L. Vázquez Acosta - Imperial College (on behalf of the LHC Higgs Cross Section WG) Thanks to M. Flechl, R. Harlander, M. Krämer, M. Spira, M. Schumacher, R. Tanaka & M. Warsinsky for the useful discussions and help preparing this talk

  2. Standard Model and Supersymmetry • The Standard Model does amazing job describing physics • at the weak scale ~100 GeV, but • Hierarchy problem in Higgs sector • If Higgs boson is fundamental particle • i) there are no high-mass particles which • couple to the Higgs field (even indirectly) • ii) Striking cancellation are needed in • high-order loop corrections to MHIGGS • SUSY at the TeV scale provides an elegant solution to hierarchy problem • - Introduces super-partners of SM particles • and cancels problematic loop corrections • - Allows light Higgs in context of GUT • without fine tuning

  3. Minimal Super-Symmetric Model • In minimal supersymmetric extension of SM there are 2 scalar doublets • Φ1 couples to down-type fermions, Φ2 to up-type fermions • → Higgs sector described by 4 masses and 2 mixing angles • 3 of 8 degrees of freedom absorbed by Z, W after EW symmetry breaking: • 5 physical Higgs bosons • β (VEVs): tan β = v2/v1 [v12+v22 = v2 = 2MZ2 /(g22+g12) = (246 GeV)2] • MSSM Higgs sector @ tree level determined by:MA & tanb • Mass hierarchies: Mh < MZ, MA < MH & MW < MH • MH,h2 = ½[ (MA2 +MZ2 ) ± ((MA2 +MZ2)2 – 4MZ2MA2 (cos22b))1/2 ] • MH+2 = MA2 + MW2 • Mh < MZ • Radiative corrections increase upper bound on Mhmax~ 130 GeV • Upper bound reached at large MA→ SM-like h • h, H (scalar, CP-even) • A (pseudo-scalar, CP-odd) • H (charged)

  4. MSSM Neutral Higgs Couplings For large tan b coupling enhanced for down-type fermions. Important for b-quarks and t since Higgs coupling proportional to mass a is a mixing angle between neutral components for two Higgs doublets H10, H20 to give the physical CP-even Higgs bosons h, H: cos2a = -cos2b [(MA2-MZ2)/(MH2-Mh2)] • For large MA→ cos(b-a) « 1 • h couplings SM-like • H coupling to W,Z suppressed tanb = 30 tanb = 5 SM Djouadi, Kalinowski, Spira

  5. CP-Conserving Benchmark Scenarios Unconstrained MSSM has large number of free parameters. Choose specific parameter points: benchmark scenarios Proposed by Carena et al., Eur.Phys.J.C26,601(2003) • Mhmax scenario • maximal Mh< 133 G eV • Conservative exclusion bounds on tan β and MA • Used at LEP/Tevatron, MSUSY= 1 TeV • No-mixing scenario • Small Mh<116GeV • No stop mixing, Xt=0, MSUSY=2TeV • Gluophobic scenario • small gh,gluon • main production channel ggh strongly suppressed • Mh<119 GeV, MSUSY=350GeV • Small-α scenario • small ghbb and ghtt • Mh<123 GeV, MSUSY=800GeV FeynHiggs curves

  6. Neutral Higgs Production Mechanisms gg fusion: dominant at small & moderate tan in comparison with associated production. Mediated by top/bottom loops (also stop/sbottom loops for M < 400 GeV) Associated production: ttonly important for h bb dominant process for large tan VBF: important when h at upper mass limit “SM-like” and H at lower mass bound. (No VBF for A at tree level) Not important for MSSM neutral Higgs production

  7. gg→f (f=h,H,A) Neutral Higgs Production Dominant MSSM Higgs production for small and moderate value of tanb - quark loops @ NLO QCD: full quark mass dependence D. Graudenz, M. Spira, and P. Zerwas, Phys. Rev. Lett. 70 (1993) 137 M. Spira, A. Djouadi, D. Graudenz, and P. M. Zerwas, Phys. B 453 (1995) 17 M. Spira, A. Djouadi, D. Graudenz, and P. Zerwas, Phys. Lett. B318 (1993) 347 R. Harlander and P. Kant, JHEP 0512 (2005) 015 • The QCD corrections increase cross section by 100% for small tanb and up to 50% in large tanb region, where bottom loop is dominant due to enhanced Yukawa couplings - quark loops @ NNLO QCD:heavy quark limit R. V. Harlander and W. B. Kilgore, Phys. Rev. Lett. 88 (2002) 201801 V. Ravindran, J. Smith, and W. L. van Neerven, Nucl. Phys. B665 (2003) 325 M. Spira, A. Djouadi, D. Graudenz, and P. Zerwas, Phys. Lett. B318 (1993) 347 R. Harlander and P. Kant, JHEP 0512 (2005) 015 C. Anastasiou, S. Beerli, S. Bucherer, A. Daleo, and Z. Kunszt, JHEP 0701 (2007) 082 U. Aglietti, R. Bonciani, G. Degrassi, and A. Vicini, JHEP 01 (2007) 021, arXiv:hep-ph/0611266. R. Bonciani, G. Degrassi, and A. Vicini, JHEP 11 (2007) 095 • Canonlybeused for small and moderatevalues of tanb - NNLL resummation: not available for the pseudo-scalar Higgs

  8. gg→f (f=h,H,A) Neutral Higgs Production • Grids of scalar and pseudo-scalar Higgs cross sections for bottom & top loops • s-top and s-bottom loops neglected so far mhmax scenario stb, sbb: NLO QCD (HIGLU - M. Spira, hep-ph/9510347) stt: NLO QCD (HIGLU) & NNLO heavy quark limit (GGH@NNLO – R. Harlander, W. Kilgore Phys.Rev.Lett. 88 (2002) 201801 & JHEP 0210 (2002) 017 ) gtMSSM/gtSM, gbMSSM/gbSM: Feynhiggs 2.7.4 S. Heinemeyer, W. Hollik, G. Weiglein Comput.Phys.Commun.124 (2000) 76 Eur.Phys.J.C9 (1999) 343 & Eur.Phys.J. C28 (2003) 133 M. Frank, T. Hahn, S. Heinemeyer, W. Hollik, H. Rzehak, G. Weiglein JHEP 0702 (2007) 47 PDF: MSTW2008 (NLO & NNLO) aS(MZ)=0.12018 (NLO), 0.11707 (NNLO) mR = mF = Mf (varied by a factor 2) LHC Higgs Cross Section Group arXiv:1101.0593 [hep-ph] PDF+aS uncertainty: 15 % Scale uncertainty: 10-15 %

  9. Feynhiggs: Yukawa Couplings & Masses Light scalar Higgs: h Pseudoscalar Higgs: A mhmax scenario top coupling top coupling tanb bottom coupling decoupling limit bottom coupling tanb P. Kant, R.V. Harlander, L. Mihaila, M. Steinhauser, JHEP 1008 (2010) 104 Light MSSM Higgs boson mass to three-loop accuracy (not used yet)

  10. Neutral Higgs: gg→A Cross Section tanb=5 tanb=10 mhmax scenario Low-medium tanb: virtual top threshold for MA = 2 mt mt=172.5 GeV tanb=50 tanb=30 Large tanb: b-loop dominant arXiv:1101.0593 [hep-ph]

  11. Neutral Higgs: gg→h Cross Section mhmax scenario tanb=5 tanb=10 MA >> MZ Decoupling limit: s ~ NNLO SM tanb=30 tanb=50 Most of the region is dominated by low MA values arXiv:1101.0593 [hep-ph]

  12. Neutral Higgs: gg→H Cross Section tanb=5 tanb=10 mhmax scenario Low-medium tanb: virtual top threshold for MA = 2mt mt=172.5 GeV tanb=50 tanb=30 Large tanb: b-loop dominant arXiv:1101.0593 [hep-ph]

  13. gg→H: SUSY NLO QCD Corrections • - SUSY QCD corrections: full mass dependence (not used yet) • C. Anastasiou, S. Beerli, and A. Daleo, Phys. Rev. Lett. 100 (2008) 241806 • M. Mühlleitner, H. Rzehak, and M. Spira, ArXiv: 1001.3214 [hep-ph] • for mhmax scenario: less than 10 % Phys. Rev. Lett. 100 (2008) 241806 Small a scenario tanb=30 ArXiv: 1001.3214 [hep-ph]

  14. gg→f Cross Section with SUSY QCD corrections NLO QCD + SUSY ( s-quark & s-gluino) QCD corrections gluophobic scenario mhmax scenario tanb=10 LHC Tevatron R.V. Harlander, F. Hofmann, H. Mantler JHEP 1102 (2011) 055 HIGLU contains SUSY QCD corrections and s-quark loops now  The QCD corrections due to gluino exchange are not yet included Next steps: • redo the cross section grids in the Yellow Report • compare to the results of Harlander et al arXiv:1101.0593 [hep-ph]

  15. Neutral Higgs: associated b production Dominant Higgs production process at high values of tanb Exclusive with four active parton flavours Calculation available at NLO 4FS S. Dittmaier, M. Kramer, M. Spira Phys. Rev. D 70, 074010 (2004) S. Dawson, C.B. Jackson, L. Reina, D. Wackeroth Phys. Rev. D 69, 74027 (2004) private code – official release in preparation Scale uncertainty: 25 - 30 % 4FS Approximation: start with at LO At NNLO contributes in the real corrections Calculation available at NNLO 5FS R.V. Harlander, W.B. Kilgore Phys. Rev. D 68, 013001 (2003) BBHATNNLO Scale uncertainty: 10 % for MH> 200 GeV PDF uncertainty: < 10 % for MH < 600 GeV 5FS

  16. Neutral Higgs: associated b production First consistent comparison between the 4FS and 5FS calculation schemes Pseudoscalar Higgs arXiv:1101.0593 [hep-ph] Scalar Higgs 4FS: scale 5FS: scale + PDF&aS 4FS: scale 5FS: scale + PDF&aS 30 % MSTW2008 4FS PDF: error sets not available at the time of the study MS bottom mass: Bottom pole mass (MSTW2008)

  17. Neutral Higgs: associated b production PDF+aS uncertainty Scale uncertainty arXiv:1101.0593 [hep-ph] Variations gives maximal/minimal cross sections 5FS: 4FS:

  18. MSSM Neutral Higgs Cross Section Summary tanb = 5 tanb = 30 mhmax scenario bbf from ggH@NNLO (5FS) Scaled by (gbMSSM/gbSM)2 from FeynHiggs arXiv:1101.0593 [hep-ph]

  19. Santander Matching: 4FS & 5FS bbH R. Harlander, M. Krämer, M. Schumacher CERN-PH-TH/2011-134 • Difference between 4FS & 5FS is logarithmic • - Large Higgs mass: 5FS more reliable • as it resums collinear logs ln(MH/mb) • use 5FS for mH→∞ • - For small logs [ln(MH/mb)=2] 4FS dominates arbitrary choice Common approach for ATLAS/CMS results

  20. CMS & ATLAS: MSSM Neutral Higgs exclusion in tanb – MA plane Higgs→ttsearch 36 pb-1 arXiv:1107.5003 [hep-ex] 1.1 fb-1 CMS-PAS-HIG-11-009 CMS restricticts to tanb < 60 Santander matching used More luminosity: larger reach in MA ATLAS: theoretical uncertainty used in limit setting procedure CMS: theoretical band in observed limit

  21. Charged Higgs Production Mechanism Two main production mechanism at the LHC • top quark decay • Associated production Suppressed modes:

  22. Light Charged Higgs Production: t→bH± mhmax scenario arXiv:1101.0593[hep-ph] FeynHiggs 2.7.3 S. Heinemeyer, W. Hollik, and G. Weiglein - Comput. Phys. Commun. 124 (2000) 76 - Eur. Phys. J. C9 (1999) 343 G. Degrassi et al. Eur. Phys. J. C28 (2003) 133–143 M. Frank et al., JHEP 02 (2007) 047 CPsuperH 2.2 J. S. Lee et al. - Comput. Phys. Commun. 156 (2004) 283 - Comput. Phys. Commun. 180 (2009) 312 t→H±b also included in HDECAY A. Djouadi, J. Kalinowski, and M. Spira, Comput. Phys. Commun. 108 (1998) 56 Not included in the comparison mu: Higgs mixing parameter FeynHiggs: CPsuperH: Good agreement between FeynHiggs & CPsuperH except for small values of mu, high tanb and small MH±

  23. Heavy Charged Higgs Production: pp→tbH± in the 4FS LO diagrams Calculation available at NLO QCD 4FS J. Diaz-Cruz and O. A. Sampayo, Phys. Rev. D50 (1994) 6820 F. Borzumati, J. Kneur, and N. Polonsky, Phys. Rev. D60 (1999) 115011 D. Miller, S. Moretti, D. Roy, and W. Stirling Phys. Rev. D61 (2000) 055011 S. Dittmaier, M. Krämer, M. Spira, and M. Walser, arXiv:0906.2648 [hep-ph] tanb = 30 arXiv:1101.0593 [hep-ph] MSTW2008 PDF 4F & 5F consistent results Used 5F for predictions and uncertainties as 4F error sets were not available 4FS tanb = 30 Scale variation: factor 3 SUSY QCD corrections taken into account rescaling bottom couplings: mbtanb/n  mbtanb/n (1-Db/b)/(1+Db) private code

  24. Heavy Charged Higgs Production: pp→tbH± in the 5FS LO diagram: NLO corrections to: Calculation available at NLO QCD 5FS E. L. Berger, T. Han, J. Jiang, and T. Plehn, Phys. Rev. D71 (2005) 115012 T. Plehn, Phys. Rev. D67 (2003) 014018 C. Weydert et al., Eur. Phys. J. C67 (2010) 617 MC@NLO PDF and aS uncertainty not computed! arXiv:1101.0593 [hep-ph] Scale variation: factor 3 5FS tanb = 30 4FS.vs.5FS MSTW 5F PDF

  25. 4th generation SM: Higgs production HIGLU Unitarity arguments: MQ4< 500 GeV Marciano, Valencia, Willenbrock, Phys.Rev. D 40 (1989) 1725 Interesting range: M between 400-600 GeV G. Kribs, et al, Phys. Rev. D76 (2007) 075016 MD4=ML4=600 GeV MU4- MD4= [ 1 + 1/5*ln(MH/115) ] * 50 GeV Enhanced ggH cross section Cross Section calculation at NLO QCD: HIGLU, BR: HDECAY • The same theory uncertainty of SM ggF (±15-20% for scale & PDF+αs) • Add ±10% theory uncertaintyfor missing EW corrrections G. Kribs, T. Plehn, M. Spannowsky, T. Tait, Phys. Rev. D76 (2007) 075016 N. Schmidt, S. Cetin, S. Istin, S. Sultansoy, Eur. Phys. J. C66 (2010) 119 C. Anastasiou, R. Boughezal, R. Furlan, JHEP 1006 (2010) 101 Q. Lin, M. Spira, J.Gau, C.S. Li, Phys. Rev. D83 (2011) 094018 X. Ruan, Z. Zhang arXiv: 1105.1634 [hep-ph] A. Rozanov, M. Vysotsky, Phys. Lett. B700 (2011) 313 SM4

  26. 4th generation SM: Branching Ratios SM HDECAY 4th generation SM Enhanced gg BR HDECAY v 4.0 M. Spira, Fortschr. Phys. 46 (1998) 203 A. Djouadi, J. Kalinowski, and M. Spira, Comput. Phys. Commun. 108 (1998) 56 A. Djouadi, J. Kalinowski, M. Mühlleitner, and M. Spira, The Les Houches 2009 proceedings

  27. 4th generation SM:Cross Sections HIGLU+HDECAY 4th generation SM SM Enhanced WW/ZZ cross sections HIGLU D. Graudenz, M. Spira, and P. Zerwas, Phys. Rev. Lett. 70 (1993) 1372 M. Spira, A. Djouadi, D. Graudenz, and P. M. Zerwas, Nucl. Phys. B453 (1995) 17

  28. Fermiophobic Higgs: Branching Ratios • EW radiative corrections unknown in fermiophobic scenario, assign ± 5 % • Higgs production cross sections: NNLO VBF & WH/ZH calculation can be used HDECAY SM fermiophobic Enhanced gg BR HDECAY v 4.0 M. Spira, Fortschr. Phys. 46 (1998) 203 A. Djouadi, J. Kalinowski, and M. Spira, Comput. Phys. Commun. 108 (1998) 56 A. Djouadi, J. Kalinowski, M. Mühlleitner, and M. Spira, The Les Houches 2009 proceedings

  29. Fermiophobic Higgs: Cross Sections • EW radiative corrections unknown in fermiophobic scenario, assign ± 5 % • Higgs production cross sections: NNLO VBF & WH/ZH calculation can be used SM HIGLU+ HDECAY Enhanced gg cross section fermiophobic HIGLU D. Graudenz, M. Spira, and P. Zerwas, Phys. Rev. Lett. 70 (1993) 1372 M. Spira, A. Djouadi, D. Graudenz, and P. M. Zerwas, Nucl. Phys. B453 (1995) 17

  30. Summary • Great progress on the theoretical side which have allowed the LHC experiments to use state-of-the-art calculations for the inclusive cross sections and branching ratios on Higgs production beyond the Standard Model • The LHC Higgs Cross Section Group has provided a framework which allows to agree on input parameters, PDF, scale and alphas uncertainties which are used both by ATLAS and CMS. This will make the future combination of the Higgs limits/discovery easier • Next challenge is to establish the best NLO MC to perform exclusive selections and determine acceptance corrections [eg. introduction of b-tagging in the study of bbH production We need a bbH MC with finite b-quark pT!] • bbZ observables under study to distinguish between 4FS/5FS

  31. BACKUP

  32. MC Generator wish-list M. Schumacher • How to generate (bb)H for inclusive and exclusive studies in • the best way • It would be nice to have the process gb→bH in MC@NLO • gg(qqbar)→ttH was implemented recently • Implementation of virtual corrections via MENLOPS in • SHERPA for  1) bb→H  and  2) gb→bH • Study of acceptance corrections for bbH, H→tt with SHERPA •  How to generate gg→H including b-quark corrections. So far • all generators use the effective ggH vertex only. The pt spectrum • of the Higgs boson might be signifcantly softer for large • b-H coupling. Implement this in SHERPA?

  33. Search for Charged Higgs: t→H±b ATLAS 35 pb-1 CMS 1 fb-1 Assuming: CMS 1 fb-1 Assuming: Low tanb High tanb

  34. bbZProduction: benchmark for 4FS and 5FS calculations MC describes well the data Measurement of: • total cross section • pt of the Z and b will be used Madgraph+Pythia Fixed flavour: 4FS NLO Dittmaier, Kramer, Spira, Dawson, Jackson, Reina, Wackeroth • massive b • 2 b (no extra jets) • 1 b with pt > 15 GeV Cross sections available in: MCFM (5FS) MC@NLO (4FS) Variable Flavour: 5FS NLO massless b Campbell, Ellis, Maltoni, Willenbrock • massless b • Inclusive Z+jets (MLM matching with up to 4 jets) Cross sections from MCFM (5FS)

  35. MSSM: mhmax scenario • Mtop=  172.5 GeV • mb(mb) MSbar= 4.213 GeV • aS(MZ)=0.119 • MSUSY =  1000 GeV • Xt  = 2000 GeV • M2 = 200 GeV • m = 200 GeV • M3 =  800 GeV soft SUSY-breaking squark mass stop mixing parameter SU2 gaugino mass parameter Higgs mixing parameter gluino mass parameter Susy loop corrections are negligible in this scenario

  36. HIGLU: Standard Model Parameters • aS (MZ)= 0.12018  2 loop • L(5)QCD= 226 MeV • PDF: MSTW2008nlo68cl • Mcharm = 1.40 GeV • Mbottom = 4.75 GeV • Mtop = 172.5 GeV • GF = 1.16637 10-5 GeV-2 • MZ = 91.1876 GeV • MW = 80.398 GeV

  37. Yukawa Couplings: Db corrections from Feynhiggs M. Spira mhmax scenario: Db corrections to the b Yukawa coupling are smaller than 10 %

  38. Heavy Higgs Cross Section C. Anastasiou, S. Buehler, F. Herzog, A. Lazopoulos, arXiv:1107.0683 • Default option in iHixs • Seymour option in iHixs • Resummation of VV→VV scattering • Improved s-ch approximation Deviations wrt zero-width approximation are +30% -20% difference in cross section for MH< 600 GeV

More Related