Cornering Higgsino at the LHC
Satoshi Shirai (Kavli IPMU) Based on H. Fukuda, N. Nagata, H. Oide, H. Otono, and SS, “Higgsino Dark Matter in High-Scale Supersymmetry,” JHEP 1501 (2015) 029, “Higgsino Dark Matter or Not,” Phys.Lett. B781 (2018) 306 “Cornering Higgsino using Soft Displaced Track”, Phys.Rev.Lett. 124 (2020) 10,101801 What is Higgsino?
Higgsino is WIMP candidate:
(pseudo)Dirac fermion
Hypercharge |Y|=1/2
SU(2)doublet
<1 TeV
2 Pure Higgsino Spectrum
two Dirac Fermions
Mass difference
~ 300 MeV
Radiative correction
3 Pure Higgsino DM is Dead
DM is neutral Dirac Fermion
HUGE spin-independent cross section
4 Pure Higgsino DM is Dead
DM is neutral Dirac Fermion
Purepure Higgsino Higgsino HUGE spin-independent cross section
5 Higgsino Spectrum (with gaugino)
With Gauginos, fermion number is violated
Dirac fermion into two Majorana fermions
6 Higgsino Spectrum (with gaugino)
7 Higgsino Spectrum (with gaugino)
Due to Majorana nature
No SI elastic cross section via Z-boson
8 [N. Nagata & SS 2015] Gaugino induced Observables
Mass splitting
DM direct detection
SM fermion EDM
9 Correlation
These observables are controlled by gaugino mass
Strong correlation among these observables
10 Correlation
These observables are controlled by gaugino mass
Strong correlation among these observables
XENON1T constraint
11 Viable Higgsino Spectrum
12 Current Status of Higgsino @LHC
13 Current Constraint(higgsino)
disappearing track
14 Current Constraint(higgsino)
XENON1T
disappearing track
15 LHC Signals
p
Meta-stable track + MET p + Soft pion? gluon
>O(10)cm
16 Current Constraint(higgsino)
XENON1T
Blind Spot disappearing track
17 LHC Signals for Blind Spot
p
Meta-stable track + MET p + Soft pion? gluon
< 18 Use Soft Track 19 Event Display 25 cm Signal BG ( Z > vv) 20 Signal P P 21 Signal P P One Soft track 22 Signal P P d0 resolution One Soft track 23 Event Display Signal BG ( Z > vv) 24 Background ● Main BG event: Mono boson production: Z > vv ● O(100) tracks per event ● Tracks tend to be soft Ks ● Most of tracks are close to each other d0 ● Secondary track: long-lived particles decay: Ks, strange baryon ● Large impact parameter ● Primary track of large angle scattering with detector material: ● Fake track with large impact parameter Fake d0 25 Background vs Signal 150 GeV Higgsino: Delta m = 500 MeV: red line Impact parameter ctau = 2 mm Delta m = 1 GeV : blue line ctau = 0.1 mm 26 Background vs Signal Signal region Signal region 150 GeV Higgsino: Delta m = 500 MeV: red line Signal region ctau = 2 mm Delta m = 1 GeV : blue line ctau = 0.1 mm 27 Background vs Signal Signal region Signal region Acceptance rate for ● Higgsino with 0.5 GeV Delta M ~ 5%. Signal region ● Background ~ 0.5% 50%: Kshort, Sigma,..., 30%: Mis-measurement, 20%: Pileup 28 Result [H. Fukuda, N. Nagata, H. Oide, H. Otono && SS, 2019] MET > 500 GeV & DV pion Run2 # of BG ~ 250. 29 Result [H. Fukuda, N. Nagata, H. Oide, H. Otono && SS, 2019] MET > 500 GeV & DV pion LZ Run2 # of BG ~ 250. 30 Summary Compressed Higgsino has phenomenological importance Higgsino DM likely provides meta-stable particles ● Complementary to DM direct detecion ● Disappearing track ● Soft tracks ● Can fill “Delta M” gap region 31 Outlook Combination with shorter disappearing track Measurement of the Mass difference Application to real data is ongoing Application to other BSM models: Slepton coannihilation, minimal DM, wino. 32 Inelastic Scattering In DM direct detection, the recoil energy is O(100) keV Mass difference < O(100) keV is excluded 33 Collider Signals of DM p, e- DM DM is invisible p, e+ DM 34 Collider Signals of DM p, e- DM DM is invisible p, e+ DM Additional objects are needed to see DM. Missing energy (MET) search gluon photon, … 35 Mono-jet Signatures 100 GeV Higgsino Even 100 GeV Higgsino cannot be probed. 36 Collider Signals of DM p, e- DM DM is invisible p, e+ DM Additional objects are needed to see DM. Missing energy (MET) search gluon photon, … New observable are needed for efficient BG reduction Decay of heavier Higgsino component 37 Full Result 38 Event Display 39 Almost Pure Higgsino Spectrum Radiative correction 40 Improving Track Reconstruction [H. Fukuda, N. Nagata, H. Otono & SS 2017] 41 Background ● Main BG event: Mono boson production: Z > vv ● O(100) tracks per event ● Tracks tend to be soft ● Most of tracks are close to each other ● Secondary track: long-lived particles decay: Ks, strange baryon ● Large impact parameter ● Primary track of large angle scattering with detector material: ● Fake track with large impact parameter 42 Event Selection “Mono-jet event” with MET>500 GeV and Signal track satisfying Acceptance rate for Higgsino with 0.5 GeV Delta M ~ 5%. Background ~ 0.5% 50%: Kshort, Sigma,..., 30%: Mis-measurement, 20% Pileup 43 ABCD Method In reality, we need data drive background estimation. Acceptance rate of Signal track is almost independent on MET. A, B, C: Control regions: D: Signal region B D S(d0) 6 By using observed data for A, B ,C we can estimate # of signal region D A C D = B x C / A 0 300 500 MET 44 ABCD Method In reality, we need data drive background estimation. Acceptance rate of Signal track is almost independent on MET. Mock data Pythia8 Run2 B D A: 103302 B: 2574 S(d0) 6 C: 10691 D: 261 A C Estimation by ABCD method: D = B x C / A 0 = 266 +-6 300 500 MET BG systematic error ~3%. 45