Higgs boson production at future colliders within the Standard Model and its
minimal supersymmetric extension is reviewed. The predictions for decay rates
and production cross sections are presented including all relevant higher-order
corrections.Comment: 5 pages, latex, 5 figures, Contribution to the proceedings of the
  International Europhysics Conference on High-Energy Physics, 19--26 August
  1997, Jersusalem, Israe

Spira, Michael

English

arXiv

Higgs boson production at future colliders within the Standard Model and its minimal supersymmetric extension is reviewed. The predictions for decay rates and production cross sections are presented including all relevant higher-order corrections.Higgs boson production at future colliders within the Standard Model and its minimal supersymmetric extension is reviewed. The predictions for decay rates and production cross sections are presented including all relevant higher-order corrections

CERN Document Server

CERN-TH/97-323hep-ph/9711394November 1997Higgs Production and Decay at Future Machines?Michael SpiraCERN, Theory Division, CH-1211 Geneva 23, SwitzerlandAbstractHiggs boson production at future colliders within the StandardModel and its minimal supersymmetric extension is reviewed. Thepredictions for decay rates and production cross sections are pre-sented including all relevant higher-order corrections.CERN-TH/97-323hep-ph/9711394November 1997? Contribution to the proceedings of the International Europhysics Conference onHigh-Energy Physics, 19{26 August 1997, Jersusalem, Israel1805: Higgs Production and Decay at Future MachinesMichael Spira (Michael.Spira@cern.ch)CERN, Theory Division, CH-1211 Geneva 23, SwitzerlandAbstract. Higgs boson production at future col-liders within the Standard Model and its minimalsupersymmetric extension is reviewed. The pre-dictions for decay rates and production cross sec-tions are presented including all relevant higher-order corrections.1 IntroductionStandard Model [SM]. The SM contains oneisospin doublet of Higgs elds, which leads tothe existence of one elementary neutral CP-even Higgs boson H [1]. Only its mass is un-known. The direct search for the Higgs bo-son at the LEP experiments excludes Higgsmasses below  77 GeV [2]. Unitarity of scat-tering amplitudes requires the introduction ofa cut-o  [3], which imposes an upper boundon the Higgs mass. For the minimal value  1 TeV the upper bound on the Higgs massis MH < 700 GeV. For   MGUT  1015GeV, the Higgs mass has to be smaller than 200 GeV.Minimal Supersymmetric Extension [MSSM].Supersymmetry provides a solution to thehierarchy problem of the SM, which arisesfor small Higgs masses. The MSSM requiresthe introduction of two Higgs doublets, whichleads to ve elementary Higgs particles: twoneutral CP-even (h;H), one neutral CP-odd(A) and two charged (H) Higgs bosons. Inthe Higgs sector only two parameters have tobe introduced, which are usually chosen astg = v2=v1, the ratio of the two vacuum ex-pectation values of the CP-even Higgs elds,and the pseudoscalar Higgs mass MA. Radia-tive corrections to the MSSM Higgs sectorare large, since the leading part grows as thefourth power of the top quark mass. They in-crease the upper limit on the light scalar Higgsmass to Mh < 130 GeV [4].2 Standard Model2.1 Decay ModesH ! f f . For MH < 140 GeV the branch-ing ratios of H ! bb (+−) reach valuesof  90% ( 10%). Above the tt thresholdthe branching ratio of H ! tt amounts to< 20%. QCD corrections to the bb; cc decaysare large, owing to large logarithmic contri-butions, which can be absorbed in the run-ning quark mass mQ(MH). Far above the Q Qthreshold they are known up to three loops[5, 6]. The NLO corrections have been evalu-ated including the full quark mass dependence[5]. They are moderate in the threshold regionMH > 2mQ.H !W+W−; ZZ. The H ! WW;ZZ de-cay modes dominate forMH > 140 GeV. Elec-troweak corrections are small in the intermedi-ate Higgs mass range, while they enhance thepartial widths by about 20% for MH  1 TeVdue to the self-interaction of the Higgs par-ticle [7]. For MH < 2MW;Z o-shell decaysH ! W W ; ZZ are important. They leadto WW (ZZ) branching ratios of about 1%for MH  100 (110) GeV.H ! γγ. The decay H ! γγ is mediatedby fermion and W -boson loops, which inter-fere destructively. The W -boson contributiondominates [8]. The photonic branching ratioreaches a level of > 10−3 for Higgs massesMH < 150 GeV. This decay mode plays asignicant ro^le for the Higgs search at theLHC forMH < 140 GeV. QCD corrections aresmall in the intermediate mass range [9].Branching ratios and decay width. The bran-ching ratios of the Higgs boson are presentedin Fig. 1. For MH < 140 GeV, where thebb; +−; cc and gg decay modes are dom-2 M. Spirainant, the total decay width is very small,Γ < 10 MeV. Above this mass value theWW;ZZ decay modes become dominant. ForMH < 2MZ the decay width amounts toΓ < 1 GeV, while it reaches  600 GeV forMH  1 TeV. Thus the intermediate Higgsboson is a narrow resonance.BR(H)bb_τ+τ−cc_ggWWZZtt-γγ ZγMH [GeV]50 100 200 500 100010-310-210-11Fig. 1. Branching ratios of the SM Higgs bosonas a function of its mass [10].2.2 Higgs Boson Production.e+e− colliders. At lower energies Higgs bosonsFig. 2. Production cross sections of SM Higgsbosons at future e+e− linear colliders [11].are dominantly produced via Higgs-strahlungo Z bosons, e+e− ! ZH, while at high en-ergies the W fusion process e+e− ! eeHdominates [11]. Electroweak corrections to theHiggs-strahlung process are moderate [12].The production cross sections at future e+e−colliders are shown in Fig. 2 for c.m. energiesof 500 and 800 GeV. They range between 1and 300 fb in the relevant mass range andprovide clean signatures for the Higgs boson.The angular distribution of Higgs-strahlung issensitive to the spin and parity of the Higgsparticle [11].LHC. Higgs boson production at the LHCσ(pp→H+X) [pb]√s = 14 TeVMt = 175 GeVCTEQ4Mgg→Hqq→Hqqqq_’→HWqq_→HZgg,qq_→Htt_gg,qq_→Hbb_MH [GeV]0 200 400 600 800 100010-410-310-210-111010 2Fig. 3. Higgs production cross sections at theLHC for the various mechanisms as a function ofthe Higgs mass [10].is dominated by the gluon fusion mechanismgg ! H, which is mediated by top and bot-tom triangle loops [9, 13]. This can be inferredfrom Fig. 3, which presents all relevant Higgsproduction cross sections as a function of theHiggs mass. The two-loop QCD correctionsincrease the production cross section by 60{90%, so that they can no longer be neglected[9]. [The QCD corrections to most of the back-ground processes at the LHC are also known.]In spite of the large size of the QCD correc-tions the scale dependence is reduced signi-cantly, thus rendering the NLO result reliable.For large Higgs boson masses the vec-tor boson fusion mechanism WW;ZZ ! Hbecomes competitive, while for intermediateHiggs masses it is about an order of magni-tude smaller than gluon fusion [14]. The QCDcorrections are small and thus negligible [15].Higgs-strahlung W =Z ! HW =Z playsa ro^le only for MH < 100 GeV. The QCD cor-rections are moderate, so that this process iscalculated with reliable accuracy [16].1805: Higgs Production and Decay 3Higgs bremsstrahlung o top quarks,gg; qq ! Htt, is sizeable for MH < 100 GeV[17]. The QCD corrections to this process areunknown, so that the cross section is uncer-tain within a factor of  2.3 MSSM3.1 Decay ModesTypical examples of the branching ratios anddecay widths of the MSSM Higgs bosons canbe found in Refs. [10, 11].! f f . For large tg the decay modesh;H;A ! bb; +− dominate the neutralHiggs decay modes, while for small tg theyare important for Mh;H;A < 150 GeV. Thedominant decay modes of charged Higgs par-ticles are H+ ! + ; tb. The QCD correc-tions reduce the partial decay widths into b; cquarks by 50%{75% as a result of the runningquark masses, while they are moderate for de-cays into top quarks [5, 6].Decays into Higgs and gauge bosons. The de-cay modes H ! hh;AA;ZA and A! Zh areimportant for small tg below the tt thresh-old. Similarly the decays H+ ! WA;Wh aresizeable for small tg and MH+ < mt + mb.The dominant higher-order corrections can beabsorbed into the couplings and masses of theHiggs sector. Below the corresponding thresh-olds decays into o-shell Higgs and gaugebosons turn out to be important especially forsmall tg [18]. The decays h;H ! WW;ZZare suppressed by kinematics and, in general,by the SUSY couplings and are thus less im-portant in the MSSM. The decay h ! γγ isonly relevant for the LHC in the decouplinglimit, where the light scalar Higgs boson h hassimilar properties to those of the SM Higgsparticle.Decays into SUSY particles. Higgs decays in-to charginos, neutralinos and third-generationsfermions can become important, once theyare kinematically allowed [19]. Thus theycould complicate the Higgs search at the LHC,since the decay into the LSP will be invisible.3.2 Higgs Boson Productione+e− colliders. Neutral MSSM Higgs bosonsFig. 4. Production cross sections of MSSM Higgsbosons at future e+e− linear colliders [11].will be produced dominantly via e+e− ! Z+h=H;A + h=H and W boson fusion e+e− !ee + h=H at future e+e− colliders. Thesize of the individual cross sections dependsstrongly on tg, but the sum is always of theorder of the SM cross section. Typical exam-ples are presented in Fig. 4 forps = 500 GeV,ranging between 1 and 100 fb [11].Charged Higgs bosons can be produced viapair production e+e− ! H+H− or throughtop quark decays e+e− ! tt ! H+bt. Theyare in general detectable, with masses up tohalf the energy of the e+e− collider [11].LHC. As can be inferred from Fig. 5, neutralMSSM Higgs bosons are dominantly producedvia gluon fusion, gg ! h;H;A, which is me-diated by top and bottom quark loops [9, 13].Only for squark masses below  400 GeV canthe squark loop contributions become signif-icant [20]. The two-loop QCD corrections in-crease the production cross sections by 10%{100% and thus cannot be neglected [9].For large tg Higgs bremsstrahlung o bquarks, gg; qq ! bb + h=H=A, dominates ina large part of the relevant Higgs mass ranges[17, 21]. The QCD corrections are unknown.Vector boson fusion WW=ZZ ! h=H andHiggs-strahlung, W =Z ! W=Z + h=H, aresuppressed in most of the parameter space by4 M. Spiraσ(pp→h/H+X) [pb]√s = 14 TeVMt = 175 GeVCTEQ4Mh/H [GeV]tgβ = 30gg→HHbb_Htt_HZHWHqqgg→hhbb_htt_hZhWhqqh Hm m50 100 200 500 100010-410-310-210-111010 210 310 4Fig. 5. Scalar Higgs production cross sections atthe LHC for the various mechanisms as a functionof the Higgs mass for tg = 30 [10].SUSY couplings compared with the SM andthus less important.References[1] P.Higgs, Phys. Rev. Lett. 12 (1964)132 and Phys. Rev. 145 (1966) 1156;F.Englert and R.Brout, Phys. Rev. Lett.13 (1964) 321; G.Guralnik et al., Phys.Rev. Lett. 13 (1964) 585.[2] P. Janot, these proceedings.[3] N.Cabibbo et al., Nucl. Phys. B158(1979) 295; M.Lindner, Z. Phys. C31(1986) 295; A.Hasenfratz et al., Phys.Lett. B199 (1987) 531; J.Kuti etal., Phys. Rev. Lett. 61 (1988) 678;M.Lu¨scher and P.Weisz, Nucl. Phys.B318 (1989) 705. M.Sher, Phys. Rep.179 (1989) 273; G.Altarelli and G.Isidori,Phys. Lett. B337 (1994) 141; J.Casas etal., Phys. Lett. B342 (1995) 171;[4] Y.Okada et al., Prog. Theor. Phys. 85(1991) 1; H.Haber and R.Hempfling, Phys.Rev. Lett. 66 (1991) 1815; J.Ellis et al.,Phys. Lett. B257 (1991) 83; M. Carenaet al., Phys. Lett. B355 (1995) 209;H.Haber et al., Z. Phys. C75 (1997) 539.[5] E.Braaten and J.Leveille, Phys. Rev.D22 (1980) 715; M.Drees and K.Hikasa,Phys. Lett. B240 (1990) 455 and (E)B262 (1991) 497.[6] S.Gorishny et al., Mod. Phys. Lett.A5 (1990) 2703; A.Kataev and V.Kim,Mod. Phys. Lett. A9 (1994) 1309; K.Chetyrkin, Phys. Lett. B390 (1997) 309.[7] J.Fleischer and F.Jegerlehner, Phys. Rev.D23 (1981) 2001; B.Kniehl, Nucl. Phys.B352 (1991) 1 and B357 (1991) 357; D.Bardin et al., JINR-P2-91-140; A. Ghin-culov, Nucl. Phys. B455 (1995) 21; A.Frink et al., Phys. Rev. D54 (1996) 4548.[8] J.Ellis et al., Nucl. Phys. B106 (1976)292; A.Vainshtein et al., Sov. J. Nucl.Phys. 30 (1979) 711.[9] M.Spira et al., Nucl. Phys. B453 (1995)17 and references therein.[10] M.Spira, CERN-TH/97-68 (to appear inFort. Phys.).[11] E.Accomando et al., hep-ph/9705442.[12] J.Fleischer and F.Jegerlehner, Nucl.Phys. B216 (1983) 469; A.Denner et al.,Z. Phys. C56 (1992) 261; B.Kniehl, Z.Phys. C55 (1992) 605.[13] H.Georgi et al., Phys. Rev. Lett. 40(1978) 692.[14] R.Cahn and S.Dawson, Phys. Lett. B136(1984) 196; K.Hikasa, Phys. Lett. B164(1985) 341; G.Altarelli et al., Nucl. Phys.B287 (1987) 205.[15] T.Han et al., Phys. Rev. Lett. 69 (1992)3274.[16] T.Han et al., Phys. Lett. B273 (1991) 167.[17] Z.Kunszt, Nucl. Phys. B247 (1984) 339;J.Gunion, Phys. Lett. B253 (1991) 269;W.Marciano and F.Paige, Phys. Rev.Lett. 66 (1991) 2433.[18] A.Djouadi et al., Z. Phys. C70 (1996) 437;S.Moretti and W.Stirling, Phys. Lett.B347 (1995) 291, (E) B366 (1996) 451.[19] A.Djouadi et al., Z. Phys. C74 (1997) 93.[20] S.Dawson et al., Phys. Rev. Lett. 77(1996) 16.[21] D.Dicus et al., Phys. Rev. D39 (1989) 751.

Higgs Production and Decay at Future Machines

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.347.8047

Higgs Production and Decay at Future Machines

Abstract

Similar works

Full text

Available Versions

CERN Document Server