STUDY OF HIGGS EFFECTIVE COUPLINGS AT ep COLLIDERS

Transcription

1 STUDY OF HIGGS EFFECTIVE COUPLINGS AT ep COLLIDERS HODA HESARI SCHOOL OF PARTICLES AND ACCELERATORS, INSTITUTE FOR RESEARCH IN FUNDAMENTAL SCIENCES (IPM)

2 The LHeC is a proposed deep inelastic electron-nucleon scattering (DIS) machine which has been designed to collide electrons with an energy from 60 GeV to possibly 140 GeV, with protons with an energy of 7 TeV. The future circular collider (FCC) has the option of colliding electronproton with the electron energy E e = 60 GeV that possibly goes up to E e = 175 GeV and with the proton energy of = 50 TeV. E p October 17 2

3 WHY EFFECETIVE FIELD THEORY? There are some reasons (Gravity, neutrino masses, baryon asymmetry, dark matter, ) to believe that the Standard Model is not the ultimate theory. the Standard Model of particle physics has been found to be a successful theory describing nature up to the scale of electroweak. The standard model is an effective theory valid at TeV scale and there must be a bigger theory. At energies below Λ, an EFT approach can be used theory. e.g Fermi theory of weak interaction standard model October 17 2

4 EFFECTIVE FIELD THEORY(EFT) In the EFT expansion all the operators are composed of all possible combinations of SM field. They have SU (3) SU (2) U (1) and Lorentz invariance. c L Y In the EFT approach, lagrangian is:. just a single operator for dimension-five term. It is violates the lepton number c c = i i h.c. SMEFT SM i i i Λ i Λ 2 i scale of new physics Wilson coefficient th dimension-six operator JHEP 1010 (2010) 085, Gradzadkowski,et al. The EFT is valid upto as scale lying around TeV scale. This approach is renormalizable order by order in the Λ Assuming baryon number conservation, 59 independent operators. E / Λ expansion. October 17 3

5 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) C L Y gauge invariant Lagrangian can be constructed from the SM fields. We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH CP F1 F2 G i October 17 4

6 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) gauge invariant Lagrangian can be constructed from the SM fields. C L Y We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH F1 F2 G i strongly interacting light Higgs sector October 17 5

7 Weak doublet of higgs Higgs boson quartic coupling Vacumum expectation value = 246 GeV Hermitian covariant derivative Electroweak field strength tensor Hermitian covariant derivative: Φ D Φ=Φ D µ Φ D ΦΦ µ µ Strong field strength tensor October 17 6

8 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) gauge invariant Lagrangian can be constructed from the SM fields. C L Y We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH F1 F2 G i strongly interacting light Higgs sector two Higgs fields and a pair of quarks or leptons October 17 7

9 October 17 8

10 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) gauge invariant Lagrangian can be constructed from the SM fields. C L Y We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH F1 F2 G i strongly interacting light Higgs sector two Higgs fields and a pair of quarks or leptons a pair of quark or lepton, a Higgs field, and a gauge boson October 17 9

11 October 17 10

12 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) gauge invariant Lagrangian can be constructed from the SM fields. C L Y We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH F1 F2 G i strongly interacting light Higgs sector gauge boson self-interactions two Higgs fields and a pair of quarks or leptons a pair of quark or lepton, a Higgs field, and a gauge boson October 17 11

13 October 17 12

14 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE GAUGE BASIS with the assumption of baryon and lepton number conservation and keeping only dimension-six operators, the most general SU (3) SU (2) U (1) gauge invariant Lagrangian can be constructed from the SM fields. C L Y We concentrate on the dimension-six interactions of the Higgs boson, fermions, and the electroweak gauge bosons in the strongly interacting light Higgs (SILH) basis conventions : = + co = SM i i SM SILH F1 F2 G i strongly interacting light Higgs sector gauge boson self-energies and self-interactions two Higgs fields and a pair of quarks or leptons a pair of quark or lepton, a Higgs field, and a gauge boson October 17 13

15 THE MOST GENERAL EFFECTIVE HIGGS LAGRANGIAN IN THE MASS BASIS After electroweak symmetry breaking arxiv: v2[hep-ph]. W ν µ W h µν lagrangian in the Mass basis W µν W h µν W µν W h µν October 17 14

16 HIGGS PRODUCTION IN THE FUTURE ELECTRON-PROTON COLLIDER Feynman diagrams for charge current Feynman diagrams for neutral current October 17 15

17 HIGGS PRODUCTION IN ELECTRON-PROTON COLLIDER ± E = 140 GeV Total produvtion cross section of SM Higgss boson in epcollisions with and e E = 7TeV, as a function of the Higgs Mass. p CERN-OPEN LHeC-Note GEN Geneva, June 13, 2012, LHeC Study Group. October 17 16

18 e p hjν e in the presence of dimension six operators The full set of interactions generated by the dimension-six operators mentioned in the Higgs Effective Lagrangian,, SILH F have been implemented in FeynRules (Alloul, Fuks,Comput. Phys. Com. 185, 2250(2014) ) 1 F2 and the model is imported to a Universal FeynRules Output (UFO) module (Alloul, Fuks and Sanz,,JHEP 1404 (2014) ), Then, the UFO model files have been inserted in the MadGraph5-aMC@NLO (J.Alwall, et al. JHEP 1407, 079 (2014).). Monte-Carlo (MC) event generator to calculate the cross sections and generate the signal events. The CTEQ6L1 PDF set ( Pumplin, et al, JHEP 0207, 012 (2002) ) is used as the proton structure functions. The renormalization and factorization scales are set dynamically by MadGraph5-aMC@NLO default. The next-to-leading order QCD correction to the signal process e p hjν e is found to be small (Jager, et al. P.R.D 81, )), Therefore, in this work the k -factor for the signal is assumed to be one. The events of signal process are generated with MadGraph5-aMC@NLO then the Higgs boson decay into a bb pair is done with MadSpin module ( Artoisenet, et al. JHEP 1303, 015 (2013) ). Pythia 6 ( Sjostrand, et al. Comput. Phys. Commun 178, 852 (2008) ) package is utilized to perform fragmentation, hadronisation, initial- and final-state parton showers. Jets are clustered using FastJet3.2.0 (Cacciari, et al. Eur. Phys. J. C 72, 1896 (2012)) with the algorithm (Soyez, arxiv: [hep-ph] ). k T October 17 17

19 Representative Feynman diagrams at tree level for the in the presence of dimension six operators e p hjν e October 17 18

20 Representative Feynman diagrams at tree level for the in the presence of dimension six operators e p hjν e The vertices which receive contributions from the are shown by filled circules. eff October 17 19

21 sensitive parameters: October 17 20

22 Backgrounds Based on the signal final state that consists of missing transverse energy, a pair of from the Higgs boson decay and a forward jet, the backgrounds include processes with three jets and large missing energy in the final state. In particular, the following processes have been taken into account : 1). bbbν e bbjν 2). 3). 4). e jjjν e t ν e 5) W jν e. jν e 6) Z. hadronic decay j = ud,, cs, j = udc,,, sb, bb October 17 21

23 Signal and Backgrounds Production and Simulation The electromagnetic and hadronic calorimeters resolutions are considered by the energy smearing of 60% And, respectively. E (GeV) 5% E (GeV) 1% The b-tagging efficiency is assumed to be 60% while mis-tag probabilities of 10% and 1% for c-quark jets and lightquark jets are considered, respectively. The tracker of the LHeC detector is expected to cover pseudorapidity range up to 3. Therefore, for the b-tagging performance is valid up to η < 3 b-jet.for the light-jets, the calorimeter coverage is considered to be η < 5 light-jet. Fernandez, et al. [LHeC Study Group], A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector, J. Phys. G 39, (2012). October 17 22

24 LHeC sensitivity Jets are reconstructed with a distance parameter for the jet reconstruction algorithm p > T jet T E > miss E > 100 T total GeV. GeV. GeV. R = 0.7. Fernandez, et al. [LHeC Study Group], A Large Hadron Electron Collider at CERN: Report on the Physics and Design Concepts for Machine and Detector, J. Phys. G 39, (2012). October 17 23

25 Higgs Mass: For E = 7TeV, E = 60GeV p e. The Higgs boson is reconstructed using the two b-tagged jets which give the closest mass to the nominal Higgs mass, 125 GeV. The figure show the reconstructed Higgs boson mass. 95 M 135 GeV Higgs October 17 24

26 Higgs + jet Mass: For E = 7TeV, E = 60GeV p e Among the light jets, the highest p T one is taken as the light flavor jet. The figure the invariant mass distribution of the Higgs+jet. 260 < M < 1000 GeV Higgs, j October 17 25

27 impacts of all cuts Cross section (in fb) for signal and background events after applied kinematic cuts used for this analysis at the LHeC with E = 7TeV, E = 60GeV. p e October 17 26

28 Sensitivity estimate 2 χ The sensitivity are obtained using a analysis over all bins of distribution. It is defined as: = ( E p ) + ( E p ) + ( E p ). Ep b jet z, b jet b jet z, b jet light jet z, light jet EpZ Z EpZ Normalized distribution for the for signal and all background processes after applying all cuts. N 2 ( f ({ c }) s ) χ ({ c }) =. n i= bins SM 2 i n i 2 i { c = c, c, c, c HL, c HQ, c, c } n H Hud HW W HW October 17 27

29 Sensitivity estimate N 2 ( f ({ c }) s ) χ ({ c }) =. n statistical uncertainty i= bins SM 2 i n i 2 ظ i number of signal events in the i-th bin SM expectationin the i-th bin { c = c, c, c, c HL, c HQ, c, c } n H Hud HW W HW 7 SM 2 = + i n i α + β n n n n n= 1 f ({ c }) s ( c c ). October 17 28

30 Results Predicted constraints at 95% C.L. on dimension-six Wilson coefficients for the LHeC with the 1 electrons energy of E = 60GeV and E = 140GeV e e, and for integrated luminosities of 300 fb and fb 1 October 17 29

31 FCC-he sensitivity bb when the couplings are varying in the range of to 0.03, the cross section at the FCC-he increases by a factor of around 5 with respect to the LHeC. October 17 30

32 Results Predicted constraints at 95% C.L. on dimension-six Wilson coefficients for the LHeC and 1 FCC-he colliders and integrated luminosity of and. 300 fb 3000 fb 1 October 17 31

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34 FCC-he sensitivity FCC-he employs the 50 TeV proton beam of a proposed circular proton-proton collider. Similar to the LHeC case, FCC-he is sensitive to and Wilson coefficients. c HW c, c, c, c HL, c HQ, c, H Hud HW W The same analysis strategy as presented for the LHeC is followed for the FCC-he. 2 The Higgs boson decay into bb pair is considered and a χ -fit is utilized to estimate the sensitivities. October 17

35 FCC-he sensitivity One of the interesting characteristics of the signal events at the FCC-he, which requires to use a particular strategy for reconstruction of the Higgs boson. At the FCC-he, Higgs bosons of the signal events are produced highly boosted. From the topological point of view, They have a different decay compared to the Higgs bosons which are not boosted. The angular separation of a bb pair produced in a Higgs boson decay can be written as: R bb 1 x(1 x) m p H T momentum fractions of the b-jets. transverse momentum of the Higgs boson October 17

36 FCC-he sensitivity two dimensional plots of angular separation of bb pair. in terms of the Higgs boson transverse momentum for signal process with c = 0.1. HW if the Higgs boson have a transverse momentum p > 300 T GeV, the angular separation between two b-jets from the Higgs decay is Then, the common jet reconstruction R bb R < 0.3. would not be usable for all of signal events. An alternative method of fat jet algorithm is applied (Butterworth, et al. Phys. Rev. Lett. 100, (2008). ) for the boosted Events. October 17

37 FCC-he sensitivity R The normalized distribution of between Two b-quarks from the Higgs boson decay for the FCC-he. The distributions for two electron energies E = 60 e and 175 GeV, and E = 50TeV proton for two signal p scenarios c = 0.1and c = 0.1. H HW The plot clearly shows that for the signal scenario of c HW,by incrasing the colliding electron beam energy from 60 GeV to 175 GeV the Higgs bosons are produced in boosted regime. October 17