Exploring Inert Scalars at CLIC

Transcription

1 Exploring Inert Scalars at CLIC Jan Kalinowski a, Wojciech Kotlarski b, Tania Robens c, Dorota Sokolowska a Aleksander Filip Żarnecki a a Faculty of Physics, University of Warsaw b Institut für Kern- und Teilchenphysik, TU Dresden c MTA-DE Particle Physics Research Group, University of Debrecen CLIC Detector and Physics Collaboration Meeting 2018 Physics and Analysis session August 28, 2018 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

2 Outline 1 Inert Doublet Model (IDM) 2 Benchmark points 3 Analysis strategy 4 IDM at first stage of CLIC Neutral scalar production Charged scalar production 5 Prospects for high energy running 6 Conclusions and Plans Results (and write-up) prepared for CLIC BSM report. A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

3 Inert Doublet Model One of the simplest extensions of the Standard Model (SM). The scalar sector consists of two doublets: Φ S is the SM like Higgs doublet, Φ D (inert doublet) has four additional scalars H, A, H ±. ( ) ( ) G ± H ± Φ S = v+h+ig 0 2 Φ D = H+iA 2 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

4 Inert Doublet Model One of the simplest extensions of the Standard Model (SM). The scalar sector consists of two doublets: Φ S is the SM like Higgs doublet, Φ D (inert doublet) has four additional scalars H, A, H ±. ( ) ( ) G ± H ± Φ S = v+h+ig 0 2 Φ D = H+iA 2 We assume a discrete Z 2 symmetry under which SM Higgs doublet Φ S is even: Φ S Φ S inert doublet Φ D is odd: Φ D Φ D. (also other SM SM) Yukawa-type interactions only for Higgs doublet (Φ S ). The inert doublet (Φ D ) does not interact with the SM fermions! The lightest inert particle is stable: a natural candidate for dark matter! We assume the neutral scalar H is the dark matter particle. m H < m A, m H ± A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

5 Inert Doublet Model After EWSB, the model contains a priori seven free parameters. Two parameters can be fixed from the Standard Model (v, m h ). We are left with five free parameters, which we take as: three inert scalar masses: m H, m A, m H ± two couplings, eg. λ 2 and λ 345 = λ 3 + λ 4 + λ 5 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

6 Inert Doublet Model After EWSB, the model contains a priori seven free parameters. Two parameters can be fixed from the Standard Model (v, m h ). We are left with five free parameters, which we take as: three inert scalar masses: m H, m A, m H ± two couplings, eg. λ 2 and λ 345 = λ 3 + λ 4 + λ 5 Inert scalars couplings to γ, W ± and Z determined by SM parameters well established predictions for production and decay rates! We scanned the IDM parameter space looking for scenarios consistent with current theoretical and experimental constraints, for masses up to 1 TeV. For details and previous IDM parameter scan results see: Agnieszka Ilnicka, Maria Krawczyk, and Tania Robens, Inert Doublet Model in light of LHC Run I and astrophysical data, Phys. Rev. D93(5):055026, 2016, arxiv: Agnieszka Ilnicka, Tania Robens, and Tim Stefaniak, Constraining Extended Scalar Sectors at the LHC and beyond, Mod. Phys. Lett. A33(n11): , 2018, arxiv: A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

7 IDM benchmark points Out of about points consistent with all considered constraints, we chose 43 benchmark points (23 accessible at 380 GeV) for detailed studies: The selection was arbitrary, but we tried to cover wide range of scalar masses and the mass splittings get significant contribution to the relic density For list of benchmark point parameters, see backup slides A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

8 Analysis strategy Production of IDM scalars at CLIC dominated by two processes: e + e A H e + e H + H Leading-order cross sections for inert scalar production processes at 380 GeV: Beam luminosity spectra not taken into account A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

9 Analysis strategy Production of IDM scalars at CLIC dominated by two processes: e + e A H e + e H + H Leading-order cross sections for inert scalar production processes at 1.5 TeV: Beam luminosity spectra not taken into account A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

10 Analysis strategy Lepton pair production can be a signature of the AH production process followed by the A decay: e + e HA HHZ ( ) HHµ + µ while the production of the different flavour lepton pair is the expected signature for H + H production: e + e H + H HHW + ( ) W ( ) HHl + l ν ν e + e Z A Z H H l l e + e Z,γ H + H W + W H H ν l ν' l' A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

11 Analysis strategy We consider two possible final state signatures: moun pair production, µ + µ, for AH production electron-muon pair production, µ + e or e + µ, for H + H production Both channels include contributions from AH and H + H production! In particular due to leptonic tau decays. Signal and background samples were generator with WHizard based on the dedicated IDM model implementation in SARAH, parameter files for benchmark scenarios were prepared using SPheno CLIC luminosity spectra taken into account (1.4 TeV scaled to 1.5 TeV) Generator level cuts reflecting detector acceptance: require lepton energy E l > 5 GeV and lepton angle Θ l > 0 mrad no ISR photon with E γ > GeV and Θ γ > 0 mrad A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

12 Neutral scalar 380 GeV Muon pair invariant mass, M µµ, as a function of the lepton pair longitudinal momentum, P µµ Z, for BP1 scenario and SM background, at 380 GeV Background dominated by muon pair production (e + e µ + µ ) at nominal energy and radiative events (e + e µ + µ γ) apply pre-selection cuts: M µµ < 0 GeV and P µµ Z < 140 GeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

13 Neutral scalar 380 GeV Distributions of the kinematic variables describing the leptonic final state Events 3 2 Events 4 3 SM [GeV] E µµ µµ p [GeV] T BP1 BP2 BP7 Events 4 Events cos Θ µµ cos φ µµ 500 fb 1 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, 2018 / 21

14 Neutral scalar 380 GeV Cut based approach Lepton pair invariant mass distribution after selection cuts 500 fb 1 pair energy E µµ < 0 GeV transverse momentum > GeV p µµ T production angle 30 < Θ µµ < 150 azimuthal distance ϕ µµ < π 2 Events [GeV] M µµ Considered IDM scenarios result in the visible event excess 15σ, 11σ and 5σ, for BP1, BP2 and BP7 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

15 Neutral scalar 380 GeV Multivariate analysis BDT classifier with 8 input variables used for selection of signal events Response distribution for µµ channel: BP1 scenario and SM background 500 fb 1 at s = 380 GeV Events 4 3 SM background IDM signal SM+IDM BDT response signal significance of about 19.5σ for BDT> 0.11 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

16 Neutral scalar 380 GeV Multivariate analysis Summary of results for the considered benchmark scenarios S+B 20 S+B 20 S/ 15 S/ m A + m H [GeV] σ(e e HHµµ X) [fb] Expected significance mainly related to the AH production cross section 5 σ observation possible for signal cross section above about 1 fb (in the µ + µ channel) neutral inert scalar mass sum below about 260 GeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

17 Charged scalar 380 GeV Distributions of the kinematic variables describing the leptonic final state Events [GeV] M eµ Events eµ p [GeV] Z SM BP1 BP3 BP6 Events 3 Events [GeV] E eµ eµ p [GeV] T 500 fb 1 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

18 Charged scalar 380 GeV Multivariate analysis BDT classifier response distribution for eµ channel: BP1 scenario and SM background 500 fb 1 at s = 380 GeV Events 4 3 SM background IDM signal SM+IDM BDT response signal significance of about 12σ for BDT> 0.13 A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

19 Charged scalar 380 GeV Multivariate analysis Summary of results for the considered benchmark scenarios S+B S/ m H ± [GeV] S+B S/ σ(e e HHeµ X) [fb] Expected significance mainly related to the H + H production cross section 5 σ observation possible for signal cross section above about 1.5 fb charged scalar masses up to about 140 GeV significant differences are visible between different benchmark scenarios, mainly depending on the mass difference between charged and neutral inert scalar A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

20 Prospects for high energy running Same analysis procedure applied for high energy CLIC running: 1500 fb 1 at 1.5 TeV and 3000 fb 1 at 3 TeV AH signature (µ + µ ) H + H signature (µ ± e ) S+B S/ GeV 1.5 TeV 3 TeV S+B S/ GeV 1.5 TeV 3 TeV m A + m H [GeV] 2m H ± [GeV] Moderate increase in discovery reach for 1.5 TeV: neutral scalar production: m A + m H < 450 GeV ( GeV) charged scalar production: m H ± < 450 GeV ( GeV) A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

21 Prospects for high energy running As for 380 GeV, significance of the observation mainly driven by the signal production cross section (in µµ or eµ channel) + integrated luminosity Significance scaled to the same integrated luminosity of 500 fb fb GeV 1.5 TeV 3 TeV fb GeV 1.5 TeV 3 TeV = S/ 500 S µµ σ = σ(e e H H µ µ X) [fb] = S/ 500 S 1 2 eµ σ = σ(e e H H eµ X) [fb] Slope of the significance vs cross section dependence can be used as a measure of the experimental sensitivity A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

22 Prospects for high energy running Ratio of the expected significance (scaled to 500 fb 1 ) to the signal cross section in the considered channel, as a function of the scalar mass splitting ] -1 [fb µµ /σ 500 S GeV 1.5 TeV 3 TeV m A - m H [GeV] ] -1 [fb eµ /σ 500 S GeV 1.5 TeV 3 TeV m H ±-m H [GeV] For both channels: sensitivity tends to be better at low mass splittings when virtual Z or W boson produced in decay chain For AH search: sensitivity decreases with energy for large mass splittings For H + H : sensitivity increases with energy for all mass differences A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

23 Conclusions Prospects for discovery of inert scalars studied for three CLIC stages, running at 380 GeV, 1.5 TeV and 3 TeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

24 Conclusions Prospects for discovery of inert scalars studied for three CLIC stages, running at 380 GeV, 1.5 TeV and 3 TeV Low mass scenarios can be observed with high significance in the di-muon channel already at the first stage of CLIC, up to m A + m H 260 GeV m H ± 140 GeV for eµ channel A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

25 Conclusions Prospects for discovery of inert scalars studied for three CLIC stages, running at 380 GeV, 1.5 TeV and 3 TeV Low mass scenarios can be observed with high significance in the di-muon channel already at the first stage of CLIC, up to m A + m H 260 GeV m H ± 140 GeV for eµ channel The discovery reach is extended to 450 GeV when running at 1.5 TeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

26 Conclusions Prospects for discovery of inert scalars studied for three CLIC stages, running at 380 GeV, 1.5 TeV and 3 TeV Low mass scenarios can be observed with high significance in the di-muon channel already at the first stage of CLIC, up to m A + m H 260 GeV m H ± 140 GeV for eµ channel The discovery reach is extended to 450 GeV when running at 1.5 TeV No improvement with 3 TeV running (cross sections too low) A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

27 Conclusions Prospects for discovery of inert scalars studied for three CLIC stages, running at 380 GeV, 1.5 TeV and 3 TeV Low mass scenarios can be observed with high significance in the di-muon channel already at the first stage of CLIC, up to m A + m H 260 GeV m H ± 140 GeV for eµ channel The discovery reach is extended to 450 GeV when running at 1.5 TeV No improvement with 3 TeV running (cross sections too low) Much higher significance can be expected for H + H production in the semi-leptonic final state (isolated lepton and two jets or one massive jet) energy and invariant mass recontruction for one of W bosons better signal-background separation much larger branching fraction compared to eµ: 2.25% 28.6% significance increase by at least a factor of 3 estimated discovery reach up to m H ± 700 GeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

28 Plans In addition to the CLIC BSM report contribution we plan to prepare e-print/paper with detailed description for benchmark selection e-print/paper with more details on IDM phenomenology at e + e colliders, covering also 250 and 500 GeV A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

29 Plans In addition to the CLIC BSM report contribution we plan to prepare e-print/paper with detailed description for benchmark selection e-print/paper with more details on IDM phenomenology at e + e colliders, covering also 250 and 500 GeV Full simulation study of selected benchmark point(s) will follow, in particular for semi-leptonic channel (looks promissing) Should we consider 380 GeV? Or go directly to 1.5 TeV? A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

30 Thank you! A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

31 Additional references Inert Doublet Model Nilendra G. Deshpande and Ernest Ma, Pattern of Symmetry Breaking with Two Higgs Doublets, Phys. Rev. D18:2574, Laura Lopez Honorez and Carlos E. Yaguna, The inert doublet model of dark matter revisited, JHEP 09:046, 20, Ethan Dolle, Xinyu Miao, Shufang Su, and Brooks Thomas, Dilepton Signals in the Inert Doublet Model, Phys. Rev. D81:035003, 20, A. Goudelis, B. Herrmann, and O. Stål, Dark matter in the Inert Doublet Model after the discovery of a Higgs-like boson at the LHC, JHEP 09:6, 2013, Software Wolfgang Kilian, Thorsten Ohl, and Jurgen Reuter, WHIZARD: Simulating Multi-Particle Processes at LHC and ILC, Eur. Phys. J. C71:1742, 2011, arxiv: Florian Staub, Exploring new models in all detail with SARAH, Adv. High Energy Phys. 2015:840780, 2015, arxiv: Werner Porod, SPheno, a program for calculating supersymmetric spectra, SUSY particle decays and SUSY particle production at e+ e- colliders, Comput. Phys. Commun. 153: , 2003, hep-ph/ Andreas Hoecker, Peter Speckmayer, Joerg Stelzer, Jan Therhaag, Eckhard von Toerne, and Helge Voss, TMVA: Toolkit for Multivariate Data Analysis, PoS ACAT:040, 2007, physics/ A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

32 Backup slide IDM benchmark points Constraints on inert scalar masses and couplings Theoretical vacuum stability at tree level perturbative unitarity global minimum of the potential Experimental (SM-like) Higgs boson mass and signal strenghts from LHC Total widths of W and Z boson Agreement with electroweak precision observables Exclusion from SUSY searches at LEP and LHC experiments. Lower limit on H ± width from long-lived charged particle searches Direct bound by the dark matter nucleon scattering (LUX, XENON1T) Planck limit on relic density A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

33 Backup slide Low mass IDM benchmark points No. M H M A M H ± λ 2 λ 345 Ω ch 2 BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP BP A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

34 Backup slide High mass IDM benchmark points No. M H M A M H ± λ 2 λ 345 Ω ch 2 HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP HP A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

35 Backup slide Signal processes for µ + µ final state e + e µ + µ HH, µ + µ ν µ ν µ HH, τ + µ ν τ ν µ HH, µ + τ ν µ ν τ HH, τ + τ HH, τ + τ ν τ ν τ HH. withτ ± µ ± νν Signal processes for e ± µ final state e + e µ + ν µ e ν e HH, e + ν e µ ν µ HH, µ + ν µ τ ν τ HH, τ + ν τ µ ν µ HH, e + ν e τ ν τ HH, τ + ν τ e ν e HH, τ + τ HH, τ + ν τ τ ν τ HH, A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21

36 Backup slide BDT input variables Input variables describing the kinematics of the dilepton final state: total energy of the muon pair, E ll ; dilepton invariant mass, M ll ; dilepton transverse momentum, p ll T ; polar angle of the dilepton pair, Θ ll ; Lorentz boost of the dilepton pair, β ll = p ll /E ll ; l production angle with respect to the beam direction, calculated in the dilepton center-of-mass frame, Θ l l production angle with respect to the dilepton pair momentum direction, calculated in the dilepton center-of-mass frame, (l, ll), reconstructed missing (recoil) mass M miss (calculated assuming nominal e + e collision energy), A.F.Żarnecki (University of Warsaw) Inert CLIC August 28, / 21