We review the prospects for Central Exclusive Diffractive (CED) production of
Higgs bosons in the SM with a fourth generation of fermions at the LHC using
forward proton detectors installed at 220m and 420m distance around ATLAS and /
or CMS. We discuss the determination of Higgs spin-parity and coupling
structures at the LHC and show that the forward proton mode would provide a
critical information on the CP properties of the Higgs bosons.Comment: 4 pages, 1 figure, talk given by S.H. at the "Physics at the LHC
  2010", May 2010, DESY Hamburg, German

Heinemeyer, S.

Khoze, V. A.

Ryskin, M. G.

Tasevsky, M.

Weiglein, G.

English

arXiv

We review the prospects for Central Exclusive Diffractive (CED) production of Higgs bosons in the SM with a fourth generation of fermions at the LHC using forward proton detectors installed at 220m and 420m distance around ATLAS and / or CMS. We discuss the determination of Higgs spin-parity and coupling structures at the LHC and show that the forward proton mode would provide a critical information on the CP properties of the Higgs bosons

Heinemeyer, Sven

Khoze, Valery A.

Ryskin, Mikhail G.

Tasevsky, Marek

Weiglein, Georg

DESY

BSM Higgs physics at the LHC in the forward proton mode

BSM Higgs Physics at the LHC in the Forward Proton Mode

DESY Publication Database

4 páginas, 1 figura.-- Trabajo presentado a la Fifth Conference on Physics at LHC celebrada en Hamburgo (Alemania) del 7 al 12 de junio de 2010.We review the prospects for central exclusive diffractive (CED) production of Higgs bosons
in the SM with a fourth generation of fermions at the LHC using forward proton detectors
installed at 220 m and 420 m distance around ATLAS and/or CMS. We discuss the
determination of Higgs spin-parity and coupling structures at the LHC and show that the
forward proton mode would provide a crucial information on the CP properties of the Higgs
bosons.Work supported in part by the European Community’s Marie-Curie Research Training Network
under contract MRTN-CT-2006-035505 ‘Tools and Precision Calculations for Physics Discoveries
at Colliders’ (HEPTOOLS).Peer reviewe

Ryskin, Misha G.

Digital.CSIC

BSM Higgs physics at the LHC in the forwardproton modeSven Heinemeyer1,Valery A. Khoze2,3, Misha G. Ryskin2,4, Marek Tasevsky5, Georg Weiglein61Instituto de F´ısica de Cantabria (CSIC-UC), Santander, Spain2IPPP, Department of Physics, Durham University, Durham DH1 3LE, U.K.3School of Physics & Astronomy, University of Manchester, Manchester M13 9PL, U.K.4Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg, 188300, Russia5Institute of Physics, 18221 Prague 8, Czech Republic6DESY, Notketraße 85, 22607 Hamburg, GermanyDOI: http://dx.doi.org/10.3204/DESY-PROC-2010-01/199We review the prospects for central exclusive diffractive (CED) production of Higgs bosonsin the SM with a fourth generation of fermions at the LHC using forward proton detec-tors installed at 220 m and 420 m distance around ATLAS and/or CMS. We discuss thedetermination of Higgs spin-parity and coupling structures at the LHC and show that theforward proton mode would provide a crucial information on the CP properties of the Higgsbosons.1 IntroductionIn the recent years there has been a growing interest in the possibility to complement the stan-dard LHC searches for a Higgs boson by the options offered by forward and diffraction physics.These assume the installation of near-beam proton detectors in the LHC tunnel installed at220 m and 420 m around ATLAS and/or CMS, see Refs. [1–6] and references therein. Thecombined detection of the centrally produced system and both outgoing protons can providevaluable information on the Higgs sector of MSSM and other popular BSM scenarios [3, 7–10].Another simple example of physics beyond the SM is a model which extends the SM by afourth generation of heavy fermions (SM4), see, for instance, [11–13]. Here it is assumed thatthe masses of the 4th generation quarks are (much) heavier than the mass of the top-quark. Inthis case, the effective coupling of the Higgs boson to two gluons is three times larger than inthe SM, and all branching ratios change correspondingly.The central exclusive diffractive (CED) processes are of the formpp→ p⊕H ⊕ p , (1)where the ⊕ signs denote large rapidity gaps on either side of the centrally produced state.However, proving that a detected new state is, indeed, a Higgs boson will be far from trivial.In particular, it will be of great importance to determine the spin and CP properties of a newstate and to measure precisely its mass, width and couplings.Following [8] we consider four luminosity scenarios: “60 fb−1” and “600 fb−1” refer torunning at low and high instantaneous luminosity, respectively, using conservative assumptionsPLHC2010 1275for the signal rates and the experimental sensitivities; possible improvements of both theoryand experiment could allow for the scenarios where the event rates are higher by a factor of 2,denoted as “60 fb−1 eff×2” and “600 fb−1 eff×2”.2 The Higgs boson in the SM4A simple example of physics beyond the SM is a model, “SM4”, which extends the SM bya fourth generation of heavy fermions, see, for instance, Refs. [11, 12, 14]. In particular, themasses of the 4th generation quarks are assumed to be (much) heavier than the mass of thetop-quark (whereas the masses of the 4th generation leptons, which do not play a role here,are less restricted). In this case, the effective coupling of the Higgs boson to two gluons isthree times larger than in the SM. No other coupling, relevant to LEP and Tevatron searches,changes significantly. Essentially, only the partial decay width Γ(H → gg) changes by a factorof 9 and, with it, the total Higgs width and therefore all the decay branching ratios, see forinstance Ref. [13, 15]. The new total decay width and the relevant decay branching ratios canbe evaluated as,ΓSM(H → gg) = BRSM(H → gg) ΓSMtot (H) , (2)ΓSM4(H → gg) = 9 ΓSM(H → gg) , (3)ΓSM4tot (H) = ΓSMtot (H)− ΓSM(H → gg) + ΓSM4(H → gg) . (4)The Higgs boson searches at LEP [16, 17] have been re-interpreted with HiggsBounds [18] inthe SM4. The bound on the SM Higgs boson at LEP of MHSM ≥ 114.4 GeV at the 95% C.L.is modified to MHSM4 ≥ 112 GeV. On the other hand Higgs boson searches in the SM4 at theTevatron [19] have been performed. The range 130 GeV <∼ MHSM4 <∼ 210 GeV is found to beexcluded. Combining the two analyses leaves us with a window of allowed Higgs masses in theSM4 of 112 GeV <∼MHSM4 <∼ 130 GeV. [GeV]HM100 120 140 160 180 200Stat. significance0246810121416182022Stat. significance 2 ×, eff. -1L = 600 fb -1L = 600 fb 2 ×, eff. -1L = 60 fb -1L = 60 fb [GeV]HM100 120 140 160 180 200Stat. significance0246810121416182022Stat. significance 2 ×, eff. -1L = 600 fb -1L = 600 fb 2 ×, eff. -1L = 60 fb -1L = 60 fbFigure 1: Significances reachable in CED Higgs production in the SM4 in the H → bb¯ (left plot)and H → τ+τ− (right plot) channel for effective luminosities of “60 fb−1”, “60 fb−1 eff×2”,“600 fb−1” and “600 fb−1 eff×2”. The regions excluded by LEP appear as blue/light grey forlow values of MHSM4 and excluded by the Tevatron as red/dark grey for larger values of MHSM4 .2 PLHC2010SVEN HEINEMEYER, VALERY A. KHOZE, MISHA G. RYSKIN, MAREK TASEVSKY, . . .76We have evaluated the significances that can be obtained in the channels H → bb¯ andH → τ+τ−. The results are shown in Fig. 1 as a function of MHSM4 for the four luminosityscenarios. The regions excluded by LEP appear as blue/light grey for low values of MHSM4and regions excluded by the Tevatron appear as red/dark grey for larger values of MHSM4 .The bb¯ channel (left plot) shows that even at rather low luminosity the remaining windowof 112 GeV <∼ MHSM4 <∼ 130 GeV can be covered by CED Higgs production. Due to thesmallness of BR(HSM4 → bb¯) at MHSM4 >∼ 160 GeV, however, the CED channel becomesirrelevant for the still allowed high values of MHSM4 , and we do not extend our analysis beyondMHSM4 ≤ 200 GeV. The τ+τ− channel (right plot) has not enough sensitivity at low luminosity,but might become feasible at high LHC luminosity. At masses MHSM4 >∼ 220 GeV it might bepossible to exploit the decay H → WW,ZZ, but no detailed analysis has been performed upto now.3 Coupling structure and spin-parity determinationThe determination of the spin and the CP properties of Higgs bosons using the standard methodsrely to a large extent on the coupling of a relatively heavy SM-like Higgs to two gauge bosons.The first channel that should be mentioned here is H → ZZ → 4l. This channel providesdetailed information about spin and CP-properties if it is open [20]. Within a SM-like set-upit was analyzed how the tensor structure of the coupling of the Higgs boson to weak gaugebosons can be determined at the LHC [21–23]. One study for MHSM = 160 GeV was based onHiggs production in weak vector boson fusion with the subsequent decay to SM gauge bosons.It was shown that the discrimination between the two extreme scenarios of a pure CP-even (asin the SM) and a pure CP-odd tensor structure is possible at a level of 4.5 to 5.3σ using about10 fb−1. A discriminating power of two standard deviations at MHSM = 120 GeV in the taulepton decay mode requires an integrated luminosity of 30 fb−1 [23].For MH ≈MA >∼ 2MW the lightest MSSM Higgs boson couples to gauge bosons with aboutSM strength, but its mass is bounded from above by Mh <∼ 135 GeV [24], i.e. the light Higgs isin a mass range where the decay to WW (∗) or ZZ(∗) is difficult to exploit. On the other hand,the heavy MSSM Higgs bosons, H and A, decouple from the gauge bosons. Consequently, theanalysis for MHSM = 160 GeV cannot be taken over to the MSSM. This shows the importanceof channels to determine spin and CP-properties of the Higgs bosons without relying on (tree-level) couplings of the Higgs bosons to gauge bosons. CED Higgs production can yield crucialinformation in this context [2, 7, 8].The MHSM = 120 GeV analysis, on the other hand, can in principle be applied to the SUSYcase. However, in this case the coupling of the SUSY Higgs bosons to tau leptons does notexhibit a (sufficiently) strong enhancement as compared to the SM case. Consequently, noimprovement over the 2σ effect within the SM can be expected. The same would be true in anyother model of new physics with a light SM-like Higgs and heavy Higgses that decouple fromthe gauge bosons.The CED production channels may provide crucial information on the CP properties ofHiggs-like states detected at the LHC, for instance via the Jz selection rule [25]. Thanks to thisselection rule in the CED case we already know that the observed new object has even parity(P = +), and the projection of its spin is Jz = 0. This knowledge will greatly simplify thedetermination of the detected new state.As discussed in [7,8] it will be challenging to identify a CP-odd Higgs boson, for instance thePLHC2010 3BSM HIGGS PHYSICS AT THE LHC IN THE FORWARD PROTON MODE277A boson of the MSSM, in the CED processes. The strong suppression, caused by the P -evenselection rule, effectively filters out its production. However, in the semi-inclusive diffractivereactions the pseudoscalar production is much less suppressed. As shown in a recent study [5]there are certain advantages of looking for the CP-odd Higgs particle in the semi-inclusiveprocess pp → p + gAg + p with two tagged forward protons and two large rapidity gaps. Theamplitude of CP-odd A boson production can be of the same order as the CP-even bosonamplitude if events with relatively hard gluons, whose energy is comparable with the energy ofthe whole gAg system, are selected.4 AcknowledgmentsWork supported in part by the European Community’s Marie-Curie Research Training Networkunder contract MRTN-CT-2006-035505 ‘Tools and Precision Calculations for Physics Discov-eries at Colliders’ (HEPTOOLS).References[1] M. Albrow and A. Rostovtsev, arXiv:hep-ph/0009336.[2] V.A. Khoze, A.D. Martin and M. Ryskin, Eur. Phys. J. C 23 (2002) 311.[3] M. Albrow, T. Coughlin and J. Forshaw, arXiv:1006.1289 [hep-ph].[4] A. De Roeck, V.A. Khoze, A. Martin, R. Orava and M. Ryskin, Eur. Phys. J. C 25 (2002) 391.[5] V. A. Khoze, A. Martin, M. Ryskin and A. Shuvaev, Eur. Phys. J. C 68 (2010) 125.[6] M. Albrow et al. [FP420 R&D Collaboration], JINST 4 (2009) T10001.[7] A. Kaidalov, V.A. Khoze, A.D. Martin and M. Ryskin, Eur. Phys. J. C 33 (2004) 261.[8] S. Heinemeyer, V. A. Khoze, M. G. Ryskin, W. J. Stirling, M. Tasevsky and G. Weiglein, Eur. Phys. J. C53 (2008) 231.[9] B. Cox, F. Loebinger and A. Pilkington, JHEP 0710 (2007) 090.[10] M. Chaichian, P. Hoyer, K. Huitu, V. A. Khoze and A. Pilkington, JHEP 0905 (2009) 011.[11] P. Frampton, P. Hung and M. Sher, Phys. Rept. 330 (2000) 263.[12] B. Holdom et al., PMC Phys. A 3 (2009) 4 [arXiv:0904.4698 [hep-ph]].[13] G. Kribs, T. Plehn, M. Spannowsky and T. Tait, Phys. Rev. D 76 (2007) 075016.[14] J. Erler and P. Langacker, Phys. Rev. Lett. 105 (2010) 031801.[15] C. Anastasiou, R. Boughezal and E. Furlan, JHEP 1006 (2010) 101.[16] G. Abbiendi et al. [ALEPH, DELPHI, L3, OPAL Collaborations and LEP Working Group for Higgs bosonsearches], Phys. Lett. B 565 (2003) 61.[17] S. Schael et al. [ALEPH, DELPHI, L3, OPAL Collaborations and LEP Working Group for Higgs bosonsearches], Eur. Phys. J. C 47 (2006) 547.[18] P. Bechtle, O. Brein, S. Heinemeyer, G. Weiglein and K. Williams, Comput. Phys. 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BSM Higgs physics at the LHC in the forward proton mode.

BSM Higgs Physics at the LHC in the Forward Proton Mode

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