Constraining h s s at lepton colliders Matthias Schla ff er - PowerPoint PPT Presentation

Constraining h → s ¯ s at lepton colliders Matthias Schla ff er Weizmann Institute of Science based on ongoing work with: J. Duarte-Campderros, G. Perez, A. So ff er GGI, Florence August 2018

Gauge boson masses Higgs is main source of electroweak symmetry breaking! ATLAS+CMS ATLAS and CMS LHC Run 1 ATLAS CMS ± 1 σ γ γ µ ± 2 σ µ X = σ BR X | meas. σ BR X | SM ZZ µ WW µ τ τ µ bb µ − 1 − 0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 Parameter value [1606.02266] Higgs couples to gauge bosons as expected Matthias Schla ff er 1

What about fermion masses? SM: economic solution, Higgs does it! h v m ψ ∝ y ⇒ ⇒ V t v m 1 ATLAS and CMS Z V W LHC Run 1 κ or F − 1 10 m v F κ b τ − 2 10 ATLAS+CMS SM Higgs boson 3 − 10 µ [M, ε ] fit 68% CL 95% CL 4 10 − − 1 2 10 1 10 10 Particle mass [GeV] [1606.02266] Matthias Schla ff er 2

However n e o m g m s r n n n o t g c w o r a a t g e u u t p p o r h o i l t m a H o e u d s c b t t | | | | | | | | | | Large mass hierarchy Mass [ eV ] 10 6 10 7 10 8 10 9 10 10 10 11 10 12 [Thanks to Gilad Perez] Matthias Schla ff er 3

Measurement of Yukawa couplings Does the SM Higgs generate fermion masses? � prod × BR ( h → X ) µ X = � SM × BR SM ( h → X ) > tth , h → ⌧⌧ , h → bb > 5 � ( X ) > h → µµ : µ µµ < 2 . 8 at 95 % CL [ATLAS: 1705.04582, CMS: 1807.06325] Lighter fermions even less constrained! Matthias Schla ff er 4

Di ffi culties i) small branching ratio Branching Ratio LHC HIGGS XS WG 2016 1 b b WW gg -1 10 τ τ c c ZZ -2 10 γ γ -3 10 Z γ [LHCHXSWG] µ µ -4 10 120 121 122 123 124 125 126 127 128 129 130 M [GeV] n e H m o g m r n n s n o t o r g c w a a t g e u u t p p o r h o m a i o l t H e u d s c b t t | | | | | | | | | | Mass [ eV ] 10 6 10 7 10 8 10 9 10 10 10 11 10 12 Matthias Schla ff er 5

Di ffi culties i) small branching ratio ii) di ffi cult final state for quarks Branching Ratio LHC HIGGS XS WG 2016 1 > quarks appear as jets b b WW > large background gg -1 10 τ τ > hard to distinguish c c ZZ -2 10 Nevertheless: γ γ h → cc will be measured at % -3 10 level at FCC-ee [1310.8361] Z γ [LHCHXSWG] µ µ What about strange? -4 10 120 121 122 123 124 125 126 127 128 129 130 M [GeV] n e H m o g m r n n s n o t o r g c w a a t g e u u t p p o r h o m a i o l t H e u d s c b t t | | | | | | | | | | Mass [ eV ] 10 6 10 7 10 8 10 9 10 10 10 11 10 12 Matthias Schla ff er 5

Exclusive decay h → φγ [1306.5770, 1406.1722] � � o o ¯ s ¯ s s s + h h � � s ) → K + ( u ¯ > Clean decay: BR ( � ( s ¯ s ) + K − (¯ us )) ≈ 50% > BUT: BR ( h → �� ) ≈ 2 × 10 − 6 [1505.03870] s ) ≈ 2 × 10 − 4 > compare BR ( h → s ¯ > only weak limit at future (hadron) colliders [1406.1722] > current limit: BR ( h → �� ) < 4 . 8 × 10 − 4 [1712.02758] Ideas to use di ff erential distributions [see e.g. 1606.09253, 1606.09621, 1609.06592, 1611.05463] Matthias Schla ff er 6

Brute force method Alternative ansatz: > FCC-ee will produce O (10 6 − 10 7 ) Higgses via e − Z Z ∗ e + h > O (200 − 2000) of which decay into strange quarks > tag strange jets > Done before in Z → s ¯ s – Measurement of the strange quark forward backward asymmetry around the Z0 peak [DELPHI Collaboration, Eur.Phys.J. C14 (2000)] – Light quark fragmentation in polarized Z0 decays [SLD Collaboration, Nucl.Phys.Proc.Suppl. 96 (2001)] Matthias Schla ff er 7

Setup and assumptions h → jj data ⇒ kinematic separation s -tagger ⇒ limit other bkg cut&count, BDT,...

Setup and assumptions h → jj data ⇒ kinematic separation s -tagger ⇒ limit other bkg cut&count, BDT,... Part I: > Clean sample with 10 7 Higgses > Only background other Higgs decays ( h → gg , bb , cc ) > We know which jets originate from the Higgs decay > Generate and shower with PYTHIA > No detector simulation Matthias Schla ff er 8

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. In which kaons can a s quark hadronize? K 0 S K ± K 0 L Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. In which kaons can a s quark hadronize? 1 / 6 vis. K ± inv. 1 / 3 Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. In which kaons can a s quark hadronize? 1 / 6 1 / 6 vis. vis. K ± K ± inv. 1 / 3 inv. 1 / 3 CC/NC/NN=9/6/1 Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Charged kaon reconstruction: > stable on detector scales > tracking e ffi ciency 95% > Particle ID 2 � bench marks e.g.: > no ID ⇡ ± K ± > ✏ K = 95% ✏ π = 12% some observable Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Charged kaon reconstruction: > stable on detector scales > tracking e ffi ciency 95% > Particle ID [TopLC17 talk by Kurata] Matthias Schla ff er 9

� Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Charged kaon reconstruction: > stable on detector scales > tracking e ffi ciency 95% > Particle ID 3.0 2.5 dE / dx resolution 2.0 10 % 1.5 7 % 6 % 1.0 5 % 0.5 4 % 0.0 [TopLC17 talk by Kurata] 0.1 0.5 1 5 10 50 100 p [ GeV ] Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Neutral K 0 s reconstruction: > Decay length ∼ 80 cm > Needs to decay to ⇡ ± within 5 mm < R < 1 m > reconstruction e ffi ciency 80% Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Neutral K 0 s reconstruction: > Decay length ∼ 80 cm > Needs to decay to ⇡ ± within 5 mm < R < 1 m > reconstruction e ffi ciency 80% softer > Keep hardest pair of kaons jet 1 K + K − K 0 K + with charge sum | q 1 + q 2 | < 2 s > Split into CC, NC and NN jet 2 K + K 0 channel s Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Impact parameter > straight extrapolation of A.U. s s s s s s s s s s tracks 100 b b b b b b b b b b c c c c c c c c c c > no vertexing gg gg gg gg gg > O (60 − 80%) of kaon can- WW* WW* WW* WW* WW* didates in b -jets stem from b -decays 50 > O (40%) of kaon candidates in c -jets stem from c -decays > smearing according to mo- Preliminary mentum and angle 0 0.01 0.02 0.03 |d | [mm] > 5 µ m uncertainty on IP 0 Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. Fragmentation functions Z ) D K ± ( x, M 2 s g [adapted from 0803.2768] Matthias Schla ff er 9

Setup for an s -tagger Ansatz: s -jets dominantly contain a prompt kaon that carries a large fraction of the jet momentum. parallel kaon momentum A.U. 0.15 Preliminary s s s s s s s s s s b b b b b b b b b b c c c c c c c c c c gg gg gg gg gg WW* WW* WW* WW* WW* 0.1 > candidates from non- s -jets are soft, especially in g -jets > here: p ( jet ) ≈ 60 GeV 0.05 0 5 10 15 20 p [GeV] || Matthias Schla ff er 9

s -tagging performance in CC channel > impact parameter d 0 < 15 µ m no particle ID 10 0 Preliminary 10 - 1 10 - 2 B � 10 - 3 10 - 4 10 - 5 0 2 4 6 8 10 12 14 cut [ GeV ] p || ss gg bb cc uu dd W Matthias Schla ff er 10

s -tagging performance in CC channel > impact parameter d 0 < 15 µ m with particle ID: ✏ K = 95% , ✏ π = 12% 10 0 Preliminary 10 - 1 10 - 2 B � 10 - 3 10 - 4 10 - 5 0 2 4 6 8 10 12 14 cut [ GeV ] p || ss gg bb cc uu dd W Matthias Schla ff er 10

Number of events > impact parameter d 0 < 15 µ m no particle ID Preliminary 10 - 2 10 - 4 BR · � 10 - 6 10 - 8 0 5 10 15 20 cut [ GeV ] p || ss gg bb cc uu dd W Matthias Schla ff er 11

Number of events > impact parameter d 0 < 15 µ m with particle ID: ✏ K = 95% , ✏ π = 12% Preliminary 10 - 2 10 - 4 BR · � 10 - 6 10 - 8 0 5 10 15 20 cut [ GeV ] p || ss gg bb cc uu dd W Matthias Schla ff er 11