Searching for a new world New Physics at the LHC and beyond LianTao Wang U. Chicago FeynRules/Madgraph School. Nov. 19, 2018. USTC HeFei.
Guardian
SM: complete yet incomplete - Complete: could be a consistent theory valid up to the Planck scale. - Incomplete: many open questions Origin of electroweak scale Dark matter Origin of CP, flavor Matter anti-matter asymmetry … - Goal of particle physics: answer these questions. - Colliders (LHC and beyond) will be crucial.
Road ahead at the LHC
We are here.
LHC is pushing ahead. Exp. collaborations are pursuing a broad and comprehensive physics program: SUSY, composite H, extra Dim, etc.
As data accumulates m = 2 TeV 14 TeV / 8 TeV low 2.5 qq q q qg 2 gg low m 1.5 / high m 1 0.5 0 0 10 20 30 40 50 60 70 80 90 100 -1 luminosity (fb ) Rapid gain initial 10s-100 fb -1 , slow improvements afterwards. Progress will become slower, harder
New directions?
stronger coupling covered by current searches heavier NP particle
stronger coupling covered by NP too heavy for LHC current searches with direct production dark sector heavier NP particle
stronger coupling covered by NP too heavy for LHC current searches with direct production dark sector heavier NP particle
Example: Long Lived particles (LLP) - Very weakly coupled to the SM. Connection with dark matter, neutrino, etc. τ - Displaced-Long lived, soft, kink, … Covered by LHC searches already. Curtin and Sundrum - Cosmological constraints from BBN: τ < 0.1 sec (10 7 m) Here, I focus on: decay length >> 10 meters
tons of models General LLP Map
Far detectors les on � MATHUSLA � ayers � ectrons � new detectors far Letter of intent: � away from the interaction region � – – � “demonstrator” � CODEX-b � DELPHI CODEX-b box � � SM SM ϕ x shield veto FASER UXA shield Pb shield IP8 Data acquisition will be moved to surface for run 3
����� ��� ����� ��� �� ��� �� � �� � �� � �� �� �������� � �� �� � �������� � ������� � � �� ������� ����� ��� �� ��� �� �� � � � � � � �� � �� � �� � �� �� �� �� �� �� �� �� �� �� �� �� ������� ������� � � �� � �� �� � �������� � Could reach τ ≈ 10 4-5 m 9 Exotic Higgs decays γ d h γ d � � � � ��� ��� � � � � �� ��� Application: Neutral Naturalness (See back-up material) For low masses, ATLAS/CMS are background limited, CODEX-b & MATHUSLA have an edge V. Gligorov, SK, M. Papucci, D. Robinson: 1708.02243 ATLAS reach: A. Coccaro, et al.: 1605.02742 S. Knapen
Far detectors les on � MATHUSLA � ayers � ectrons � Have we fully optimized LLP searches at Letter of intent: � the interaction points ATLAS, CMS, LHCb? � – – � “demonstrator” � CODEX-b � DELPHI CODEX-b box � � SM SM ϕ x shield veto FASER UXA shield Pb shield IP8 Data acquisition will be moved to surface for run 3
Optimal place to catch LLP ΔΩ L Δ L Number of particle decayed within detector volume: 4 π × Δ L # in ≃ # produced × ΔΩ d e − L / d d = γ c τ decay length d ≫ Δ L , L Very long lived: d ≥ 100s meters
Optimal place to catch LLP Number of particle decayed within detector volume: 4 π × Δ L # in ≃ # produced × ΔΩ d e − L / d d = γ c τ ATLAS/CMS (LHCb) Far detectors ∼ 4 π < 0.1 ΔΩ Δ L 1 − 10 meters 1 − 10 meters L 1 − 10 meters 10 − 100 meters
Optimal place to catch LLP # in ≃ # produced × ΔΩ 4 π × Δ L d e − L / d d = γ c τ ATLAS/CMS (LHCb) Far detectors ΔΩ ∼ 4 π < 0.1 Δ L 1 − 10 meters 1 − 10 meters L 1 − 10 meters 10 − 100 meters Advantage of far detector? Far away from interaction point, less background. New proposal: use timing information Significantly lower background near interaction point.
Time delay a b Timing layer ` a ` SM L T 2 ` X L T 1 SM X Good for massive LLP produced with small or moderate boost β X < 1
Basic topologies X = LLP SM X SM X Y SM X or SM SM X or SM γ ≃ m Y boost: boost: γ ∼ 1 2 m X challenging for m X ≪ m Y slow moving, sizable Δ t benchmark: SUSY benchmark: Higgs portal Y = Higgs X = neutralino χ 0 → gravitino + . . . Long lived Long lived X → SM
Sensitivity to Higgs portal Jia Liu, Zhen Liu, LTW Precision Timing Enhanced Search Limit ( HL - LHC ) 10 0 10 - 1 h < 3.5 % BR inv 10 - 2 BR ( h → XX ) 10 - 3 h → X X, X → j j MS ( 30ps ) , Δ t > 0.4ns 10 - 4 MS ( 200ps ) , Δ t > 1ns EC ( 30ps ) , Δ t > 1ns 10 - 5 MS2DV, noBKG MS1DV, optimistic 10 - 6 m X in [ GeV ] 10 40 50 10 - 7 10 - 3 10 - 2 10 - 1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 c τ ( m ) For example, for BR( h → XX ) ∼ 10 − 3 EC(MS) reach can be c τ ∼ 10 3 (10 4 ) meters
Sensitivity to SUSY Jia Liu, Zhen Liu, LTW Precision Timing Enhanced Search Limit ( HL - LHC ) 10 5 F = 10 5 TeV GMSB Higgsino 10 4 Δ t > 1.2 ns 10 3 Δ t > 2 ns Δ t > 1 ns 10 4 10 2 Δ t > 10 ns c τ ( m ) MS 10 1 n bkg = 100 n bkg = 0 10 3 EC 10 0 n bkg = 100 n bkg = 0 10 - 1 10 - 2 8 TeV 13 TeV Diplaced Dijet 10 - 3 200 400 600 800 1000 1200 1400 m X ( GeV ) Slower moving LLP , timing cuts can be further relaxed.
stronger coupling covered by NP too heavy for LHC current searches with direct production dark sector heavier NP particle
Revealing trace of new physics with precision measurements
Higgs Standard Model-like Agree to about 10-20%
Not entirely surprising - In general, deviation induced by new physics is of the form δ ' c v 2 M NP : mass of new physics c: O( 1) coefficient M 2 NP Current LHC precision: 10% ⇒ sensitive to M NP < 500-700 GeV At the same time, direct searches constrain new physics below TeV already. Unlikely to see O(1) deviation.
Significant improvement with high lumi 4-5% on Higgs coupling, reach TeV new physics
Precision measurement with distribution no rate beyond this broad resonance long tails SM E Low S/B, systematic dominated. Room to improve.
Diboson production at the LHC q ¯ q → V V, V = W, Z, h. V L V L , h New physics contribution 1 New physics effect encoded in the Λ 2 O non-renormalizable operators: Λ : new physics scale
Precision measurement at the LHC possible? LEP precision tests probe NP about 2 TeV ∼ m 2 δσ Λ 2 ∼ 2 × 10 − 3 W → Λ ≥ 2 TeV σ SM At LHC, new physics effect grows with energy ∼ E 2 δσ E ∼ 1 TeV , Λ ∼ 2 TeV Λ 2 ∼ 0 . 25 σ SM LHC needs to make a 20% measurement to beat LEP LHC has potential.
Picking final state important At LHC, interference with SM crucial Signal-SM interference Without interference ∼ E 2 ∼ E 4 δσ δσ Λ 2 ∼ 0 . 25 Λ 4 ∼ 0 . 05 σ SM σ SM 1. WZ final states, only longitudinal mode useful 2. W/Z+h
Will be challenging SM WW, WZ processes are dominated by transverse modes New technique such as polarization tagging of W/Z crucial Wh/Zh(bb) channels have large reducible background Difficult measurement. Large improvement needed. Room for developing new techniques
Operators: d=6
Projections ����� �� ������ Δ ��� ∈ [ � % ��� %] � � � = � ���� ���� ( 3 ) = 1, L = 3 ab - 1 c q L Λ �� % [ ��� ] ���� ( 3 ) = 1, L = 300 fb - 1 c q L O W + O B , LEP S - parameter c 3 W = 1, L = 3 ab - 1 c 3 W = 1, L = 300 fb - 1 ���� O HW - O HB , HL - LHC h → Z γ c HB = 1, L = 3 ab - 1 ( 3 ) q , LEP δ g Zb L b L O L ���� c HB = 1, L = 300 fb - 1 � �� ( ���� ) �� ( ���� ) �� ( ���� ) �� ( ���� ) Possible to reach 4 TeV. D. Liu, LTW Better than LEP , and many LHC direct searches See also: Alioli, Farina, Pappadopulo, Ruderman, Franceschini, Panico, Pomarol, Riva, Wulzer, Azatov, Elias-Miro, Regimuaji, Venturini
Beyond LHC
来自中国的建议 • 年 月“第二届中国高能加速器物理战略发展研讨会”提出了 建造周长为 环形加速器的建议： Future Colliders – ：质心能量为 的高能正负电子对撞机 工厂） CLIC – ：在同一隧道建造质心能量为 的强子对撞机。 ILC in Japan • 年 月 日香山会议共识：“环形正负电子对撞机 工 厂 超级质子对撞机 是我国高能物理发展的重要选项 和机遇” • 年 月 日“第三届中国高能加速器物理战略发展研讨会”结 论：“环形正负电子对撞机 工厂 超级质子对撞机 Circular. “Scale up” LEP+LHC 是我国未来高能物理发展的首要选项” ~100 TeV pp collider FCC-hh (CERN), SppC(China) e � e + Higgs Factory 250 GeV FCC-ee (CERN), CEPC(China)
Ambitious program FCC-ee: ∼ 10 6 Higgses, ∼ 10 13 Zs, . . . 13 yr run plan: Higgs=3, Z=4, top=5, W=1
Currently, no plan to scan the ttbar threshold.
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