Post on 23-Jun-2020
The LHeC as a Higgs Facility
EPS HEP 2013 Stockholm, July 20th, 2013
Uta Klein (University of Liverpool) for the LHeC Study Group
A Large Hadron Electron Collider at CERN J. Phys. G: Nucl. Part. Phys. 39 (2012) 075001 [arXiv:1206.2913]
EPS2013, Uta Klein, Higgs@LHeC 2
CDR : About 200 experimentalists and theorists from 69 insStutes
Supported by CERN, ECFA, NuPECC
ContribuSons at EPS2013: An energy recovery electron accelerator for DIS at the LHC by Daniel Schulte High Precision DIS with the LHeC by Amanda Cooper-‐Sarkar The LHeC as an energy fronSer eA collider by Max Klein A new detector for deep inelasSc physics by Peter Kostka et al. (poster) New Physics with the LHeC by Monica d’Onofrio et al. (poster)
h^p://cern.ch/lhec
Physics at a glance
EPS2013, Uta Klein, Higgs@LHeC 3
! LHeC : up to 100 to 1000 <mes HERA luminosity! (no pile-‐up)
! Higgs@HERA σ~0.5 I …
! Higgs@LHeC with S/N~1; σ~200 I
! High precision proton PDFs, also for LHC searches
! High precision αS to 0.1% challenging laWce QCD…
√s=1.3-‐2 TeV
Light SM Higgs producSon in ep
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CC NC
• Scale dependencies of the LO calculaSons are in the range of 5-‐10%. • NLO QCD correcSons are small, but shape distorSons of kinemaSc distribuSons up to 20%. QED correcSons up to -‐5%.
[J. Blumlein, G.J. van Oldenborgh , R. Ruckl, Nucl.Phys.B395:35-‐59,1993] [B.Jager, arXiv:1001.3789]
Light SM Higgs producSon in ep
ETmiss electrons à
LHC protons à Fwd jet
WWH
electrons à
LHC protons à Fwd jet
FS electron
ZZH
è In ep, direc<on of quark (FS) is well defined.
EPS2013, Uta Klein, Higgs@LHeC 5
Electron beam energy
CC e-‐p
CC e+p
NC e-‐p
cross secSon [f]
109
58 20
polarised cross secSon [f] P=-‐80%
196 N.A. 25
Ee=60 GeV : √s= 1.3 TeV
MH=125 Ge
V
Hà bb study: Analysis framework
n Calculate cross sec<on with tree-‐level Feynman diagrams (PDF CTEQ6L1)
n Generate final state of outgoing par<cles
Event genera<on
by MadGraph/MadEvent
• SM Higgs produc<on • CC & NC background
• Fragmenta<on • Hadroniza<on
Fast detector simula<on by PGS (LHC-‐style detector)
H → bb selec<on
Input parameters for ini<al studies (CC e-‐p) for the CDR (before Higgs discovery):
n 150 GeV electron beam [ 60 GeV configura<on as comparison]
n 7 TeV proton beam n 120 GeV SM Higgs boson mass
Generator level cuts n pT > 5 GeV (for partons besides b) n |η| < 5.0 n For NC: Number of b quarks ≧ 2
by PYTHIA (modified for ep)
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Generated samples Background (examples)
CC: 3 jets (~57 pb) CC: single top produc<on (~4.1 pb)
CC: Z produc<on (~0.11 pb)
NC: b pair produc<on (~1.1 nb)
Signal
CC: H → bb (BR ~ 0.7 at MH=120GeV)
σ~ 0.16 pb at √s=2.05TeV
NOTE: Background sample numbers are a}er pre-‐selec<on in generator
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SelecSon of H→bb n NC DIS rejec<on
n Exclude electron-‐tagged events n ET,miss > 20 GeV n Njet (pT > 20 GeV) ≧ 3 n ET,total > 100 GeV n yJB < 0.9, Q2
JB > 400 GeV2
n b-‐tag requirement n Nb-‐jet (pT > 20 GeV) ≧ 2
n Higgs invariant mass n 90 < MH < 120 GeV
n Single top rejec<on n Mjjj,top > 250 GeV n Mjj,W > 130 GeV
ETmiss cut b-tag requirement
H→bb CC BG NC BG
⇒ 44% of remaining BG is single-‐top…
⇒10% mis-‐ID
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H→bb results [MH=120 GeV, Ep=7 TeV] Forward jet η tag H → bb signal n Forward jet tagging
n ηjet > 2 (lowest η jet excluding b-‐tagged jets)
n Higgs invariant mass a}er all selec<on
H→bb CC BG NC BG
Coordinate: Fwd: +z-‐axis along proton beam
Z→bb
Ee=150 GeV
10 I-‐1
Clear signal obtained with cut-‐and-‐count based analysis!
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H→bb results [MH=120 GeV, Ep=7 TeV]
Ee=60 GeV
Ee = 150 GeV (10 f-‐1)
Ee = 60 GeV (100 f-‐1)
H → bb signal 84.6 248
S/N 1.79* 1.05
S/√N 12.3 16.1
10 I-‐1
n Case study for electron beam energy of 60 GeV using same analysis strategy n luminosity values of 100 I-‐1 are feasible
n Electron energy recovery LINAC with high electron polarisa<on of 80% and 1034 cm-‐2 s-‐1 è enhancement by factor 18 feasible, i.e. around 4500 Higgs candidates for Ee=60 GeV allowing to measure Hbb coupling with 0.8 % sta<s<cal precision.
n S/N ~1 confirmed in independent analysis for MH=125 GeV for Ee=60 GeV (master thesis by Sergio Mandelli, University of Liverpool 2013)
*Note: A parton-‐level study delivered S/N of 4.7.
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… as a Higgs “Facility” @ 1 ab-‐1 à for first Sme a realisSc opSon of an 1 ab-‐1 ep collider (stronger e-‐source, stronger focussing magnets) and excellent performance of LHC (higher brightness of proton beam); ERL : 960 superconduc<ng cavi<es (20 MV/m) and 9 km tunnel [arXiv:1211.5102, arXiv:1305.2090; talk by D. Schulte]
EPS2013, Uta Klein, Higgs@LHeC 11
Ul<mate e and p beams, 10 years of opera<on
è other BR’s started to be explored, e.g. ττ
Measure CP properSes of Higgs • Higgs couplings with a pair of gauge bosons (WW/ZZ) and a pair of heavy fermions
(t/b/τ) are largest. • Higgs@LHeC allows uniquely to access HWW vertex è explore the CP proper<es
of HVV couplings: BSM will modify CP-‐even (λ) and CP-‐odd ( λ’) states differently
• Study shape changes in DIS normalised CC Higgsà bb cross sec<on versus the azimuthal angle, ΔφMET,J, between ET,miss and forward jet.
In ep, full Δφ range can be explored, here not shown yet.
è
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CDR iniSal study of HWW vertex: CP couplings probed to λ~0.05 λ’~0.2 based on 50 f-‐1
Partons for LHC Higgs
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50
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58
60
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
à Using LHeC input: experimental uncertainty of predicted LHC Higgs cross sec<on is strongly reduced to 0.4% due to PDFs and αS è clear Higgs mass sensi<vity in cross sec<on predic<ons. è Higgs@LHC with
σ(H)~50 pb è HL-‐LHC + ep Higgs
potenSal and PDFs and αS : transform the LHC facility into a genuine Higgs factory
LHeC
Summary
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! LHeC, in ep(A) collisions synchronous with pp (AA) running, could deliver
fundamentally new insights on the structure of the proton (and nucleus) and the strong coupling αS with high precision è thus strengthen enormously the HL/HE-‐LHC physics case for searches [“On the Rela<on of the LHeC and the LHC”, arXiv:1211.5102]
! Sensi<vity to H→bb is es<mated by an ini<al simula<on study : LHeC has the poten<al to measure H → bb coupling with an S/N of ~1 and to 1% (4%) accuracy with 60 GeV electron beam based on a luminosity of 1034 (1033) cm-‐2 s-‐1.
! At LHeC, various Higgs boson decays and Higgs CP eigenstates could be accessed via WW and ZZ fusion at c.m.s. energies of 1.3 TeV and with 1 ab-‐1 -‐ complementary to LHC experiments.
! New high luminosity prospects in ep have just started to be explored and
open exciSng new potenSal for complementary, precision Higgs physics at the LHC facility.
AddiSonal material
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CDR review process
16
International referees invited by CERN
… put to scale
17
è synchronous running of ep and pp a}er LS3 as an upgrade op<on of the HL-‐LHC
18
60 GeV Electron Accelerator
ICHEP LHeC Max Klein 7.7.2012 18
Two 1km long LINACs connected at CERN territory Arcs of 1km radius: ~9km tunnel 3 passages with energy recovery
John Osborne (June LHeC Workshop)
LHeC and the HL-‐LHC (SUSY searches)
19
With high energy and luminosity, the LHC search range will be extended to high masses, up to 5 TeV in pair produc<on. At correspondingly high x (> 0.5) the PDFs are unknown to a considerable extent à PDF uncertain<es easily > 100% for high mass searches è gluon density from LHeC (10% at x=0.6, ~4TeV)] The HL-‐LHC (search) programme requires a much more precise understanding of QCD, which the LHeC provides (strong coupling, gluon, valence, factorisa<on, satura<on, diffrac<on..)
KinemaSc distribuSons [MH=120 GeV, Ee=150 GeV, Ep=7 TeV]
a-‐b) Kinema<c distribu<ons of generated Higgs c-‐d) Reconstructed yJB and Q2
JB
pTH ηTH
yJB Q2JB
Generated events passed to Pythia and to generic LHC-‐style detector: n Coverage:
n Tracking: |η| < 3 n Calorimeter: |η| < 5
n Calorimeter resolu<on n EM: 1% ⊕ 5%/√E n Hadron: 60%/√E n Cell size: (Δη,Δφ) = (0.03, 0.03)
n Jet reconstructed (cone ΔR=0.7) n b-‐tag performance
n Flat efficiency for |η| < 3 n Efficiency/mis-‐ID
n b-‐jet: 60% n c-‐jet: 10% n Other jets: 1%
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‘Detector’ LHC ! parameter set name 320 ! eta cells in calorimeter 200 ! phi cells in calorimeter 0.0314159 ! eta width of calorimeter cells |eta| < 5 0.0314159 ! phi width of calorimeter cells 0.01 ! electromagnetic calorimeter resolution const 0.2 ! electromagnetic calorimeter resolution * sqrt(E) 0.8 ! hadronic calolrimeter resolution * sqrt(E) 0.2 ! MET resolution 0.01 ! calorimeter cell edge crack fraction cone ! jet finding algorithm (cone or ktjet) 5.0 ! calorimeter trigger cluster finding seed threshold (GeV) 1.0 ! calorimeter trigger cluster finding shoulder threshold (GeV) 0.5 ! calorimeter kt cluster finder cone size (delta R) 2.0 ! outer radius of tracker (m) 4.0 ! magnetic field (T) 0.000013 ! sagitta resolution (m) 0.98 ! track finding efficiency 1.00 ! minimum track pt (GeV/c) 3.0 ! tracking eta coverage 3.0 ! e/gamma eta coverage 2.4 ! muon eta coverage 2.0 ! tau eta coverage
20%à 5% 80%à60%
jets: cone<0.7
Disclaimer : PGS of LHC detector + flat b-‐tagging in the full tracking range of |η|<3.0 b: 60%, c: 10%, udsg: 1% CAL coverage un<l |η|<5.0 EPS2013, Uta Klein, Higgs@LHeC 21