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Martin zur Nedden, HU Berlin 1Physics at the LHC, Academic Training DESY Zeuthen June 2007
Physics at the LHC
Academic Training, Part 4:Higgs Search and Beyond Standard Model
Dr. Sven Moch, DESY Zeuthen (Theory)
Dr. Martin zur Nedden, HU Berlin (Experiment)
June 2007 DESY Zeuthen, based on a lecture in WS 06/07 at Humboldt University Berlin
Martin zur Nedden, HU Berlin 2Physics at the LHC, Academic Training DESY Zeuthen June 2007
Plan
● LHC: Experimental Overview and
Standard Model Physics (Part 3)– Monday, June 11, 2007, 9.00 - 10.30
● LHC: Higgs Searches and
Physics beyon the Standard Model (Part 4)– Thursday, June 14, 2007, 10.00 – 11.30
Martin zur Nedden, HU Berlin 3Physics at the LHC, Academic Training DESY Zeuthen June 2007
Contents
● Discoveries at the energy frontier● Overview: LHC and its experiments● Hadron-Hadron interactions● Jets: fragmentation, signature and algorithms● Standard model channels at LHC● top-physics and heavy flavor reconstruction● Higgs: event topologies and search strategies● SUSY: searches in the MSSM
Martin zur Nedden, HU Berlin 4Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Searches
● Yukava-coupling, masses of fermions● experimental evidence:
– production
– decays and search channels
● results from TEVATRON● searches at LHC
Martin zur Nedden, HU Berlin 5Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Mechanism in the Standard Model
• Doublet Φ of scalar Higgs fields H(x) exists due to the massive gauge field W,Z and the massless γ
• Complex fields Φ+ , Φ0
4 real components Φ1, …Φ4, produce mass in symmetry breaking due to self-interaction
• Goldstone/Higgs-mechanism: 3 components absorbed in the longitudinal
polarization of the massive 3 Wi-bosons• 1 physical state H remains • coupling to mass with gffH
• No prediction of Higgs mass by SM
00
2
1H
HgHff
Martin zur Nedden, HU Berlin 6Physics at the LHC, Academic Training DESY Zeuthen June 2007
Yukava coupling, Mass of Fermions
),,( 0
0L
eRRLe eeeeGL
)(22)(
0
2
1xheeee
Geeeev
GL
xhv LRRLe
LRRLe
)(2
xheev
meemL
vGm e
ee
e
mnew term in Lagrangien needed: excluded due to gauge invariance
eR(T=0, Y=-2)
eL(T=1/2, Y=-1)
h0 (T=1/2, Y=1)
igme/(2MW)igMW
W
W
(Singlet in I,Y)
choose:
Coupling to the higgs field
h0
Martin zur Nedden, HU Berlin 7Physics at the LHC, Academic Training DESY Zeuthen June 2007
Consequences from Yukava-Coupling
● electron gets mass● neutrino rest massles● strength of coupling proportional to the mass of the
fermion● mass is not predicted by the theory● masses for quarks:
– same formalism as for leptons
– difference: both quarks within the doublet have mass● new Higgs Doublet Φc
Martin zur Nedden, HU Berlin 8Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs-Production in Hadron-Hadron Interactions
gluon-gluon interaction (LHC/TEVATRON):big production cross section,decay in 2 gammas
gluon-gluon interaction (LHC/TEVATRON):production cross section very small
quark-antiquark interaction (TEVATRON):big production cross section at 2TeV (TEVATRON)decay: W,Z leptons
quark-quark interaction (LHC):big production cross section at 14TeV (LHC)decay: W,Z 2 γ (or leptons)
Martin zur Nedden, HU Berlin 9Physics at the LHC, Academic Training DESY Zeuthen June 2007
Decay Width of Different Higgs Channesl
2
3
2
22
)4
1(24
)(H
fHfFc M
mMmGNffH
)124
1()41(28
)(4
4
2
22
1
2
23
H
W
H
W
H
WHF
M
M
M
M
M
MMGWWH
)124
1()4
1(216
)(4
4
2
22
1
2
2
2
2300
H
Z
H
Z
H
Z
Z
WHF
M
M
M
M
M
M
M
MMGZZH
2
2
2
2
22
3
32
)()(32128
)(H
WW
H
qqq
q
HF
M
MI
M
mIe
MGH
Calculations in the standard model:
Martin zur Nedden, HU Berlin 10Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs – Decay Channels
(H VV) ~ GF M3H
(H γγ) ~ α2 GF M3H
(H ff) ~ GF m2f MH
Martin zur Nedden, HU Berlin 11Physics at the LHC, Academic Training DESY Zeuthen June 2007
Possible Higgs Decays / coupling constants
ffH 0
WWH 0
/0 ggH
WW
f
Hff M
emg
sin2
W
WWWH
eMg
sin
WW
ZZZH
eMg
cossin
22
1
2
2
)2(228 WFWWHF
W
MGgG
M
g
Martin zur Nedden, HU Berlin 12Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Search Strategies
bbHZpp *
Good channel for TEVATRON:
M(H) > 135 GeV: H WWM(H) < 135 GeV: H bb
gg-fusion dominant at all Higgs masses, not to separate from BG at M < 135 GeV
qq: Higgs-Strahlung: small contribution, but god to separate from BG
Martin zur Nedden, HU Berlin 13Physics at the LHC, Academic Training DESY Zeuthen June 2007
Cross Sections at TEVATRON
Martin zur Nedden, HU Berlin 14Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Search at TEVATRON, upper Limit
signal: 2 b-Jet + MET + 2 leptons
if M(H) > 135 GeV
Martin zur Nedden, HU Berlin 15Physics at the LHC, Academic Training DESY Zeuthen June 2007
Upper Limit for Higgs production at TEVATRON
if M(H) < 135 GeV
Martin zur Nedden, HU Berlin 16Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Decay Channels: Branching Ratios
Martin zur Nedden, HU Berlin 17Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Decay in the Standard Modell
fermions
bosons
decay width branching ratio
Martin zur Nedden, HU Berlin 18Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Cross Sections at LHC
gluon-gluon fusion
vector boson fusion
Martin zur Nedden, HU Berlin 19Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs: Signal to background ratio at LHC
for M(Higgs) = 150 GeV:
S/B < 10-10
Martin zur Nedden, HU Berlin 20Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs to 2 Z and 4 Leptons
CMS TDR
Very clean an good measurabe event signature:4 high pT leptons, 2 invariant masses at MZ
Martin zur Nedden, HU Berlin 21Physics at the LHC, Academic Training DESY Zeuthen June 2007
Gluon-Gluon Fusion to 4 Leptonen (Atlas/LHC)
Atlas TDR
invariant masse (ZZ 4 l)
Background, not todistinguish from Higgs-Signal:qq ZZ 4 leptons
Martin zur Nedden, HU Berlin 22Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs to 2 Gamma
CMS
also very clean signature, but small cross section:2 high pT isolated EMC-clusters
Martin zur Nedden, HU Berlin 23Physics at the LHC, Academic Training DESY Zeuthen June 2007
Gluon/Gluon Fusion to 2 Gamma (Atlas/LHC)
ATLAS TDR
Background:Not reducable: pp γγXReducable: pp γJγJ
Martin zur Nedden, HU Berlin 24Physics at the LHC, Academic Training DESY Zeuthen June 2007
Vektor-Boson Fusion: Decay to 2 W-Bosons
H WW e
Atlas TDRH WW l l υ υ (l υ qq )
Signature:Jets + 2 high pT leptons + MET
No mass peak (MET from neutrino), calculate the transverse mass
Background:tt, Wt, WWJJ production
Martin zur Nedden, HU Berlin 25Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs to 2 Tau
H ττ e :
H ττ l l + 4ν (l +J +3ν)
Atlas TDR
2 high pT leptons, big MET
Mass reconstruction possible, even with high MET
Background:Zjj , tt
Martin zur Nedden, HU Berlin 26Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Discovery potential of LHC/ATLAS
Dependency on Higgs mass and decay channel
Martin zur Nedden, HU Berlin 27Physics at the LHC, Academic Training DESY Zeuthen June 2007
Discovery potential of ATLAS/LHC
Dependency of Higgs-mass and Luminosity
Martin zur Nedden, HU Berlin 28Physics at the LHC, Academic Training DESY Zeuthen June 2007
SUper SYmmetry
● “Beyond the Standart Model”● introduction into SUper SYmmetry● Minimal Super Symmetric extension of the
standard Model (MSSM)● super symmetric interactions● SUSY breaking● particle spectra of SUSY (phenomenology)● SUSY searches
Martin zur Nedden, HU Berlin 29Physics at the LHC, Academic Training DESY Zeuthen June 2007
Global Fit of Standard Model Parameter
Martin zur Nedden, HU Berlin 30Physics at the LHC, Academic Training DESY Zeuthen June 2007
Weinberg Angle and Higgs-Masse
Martin zur Nedden, HU Berlin 31Physics at the LHC, Academic Training DESY Zeuthen June 2007
Standard Model Symmetry
• SM describes strong and electroweak interactions, L/R asymmetry• Based on symmetries and gauge invariance• All forces propagated by exchange of gauge fields (local gauge fields)
YLC USUSU )1()2()3( Gauge-Bosons (Spin = 1):
gluons Gaμ SU(3) (8,1,0)
vector bosons Wiμ SU(2) (1,3,0)
abelian boson Bμ U(1) (1,1,0)
Fermions Spin = ½:
quarks [Uiα,Di
α]L (3,2,1/3)quarks [Ui
α]R (3,1,4/3)quarks [Di
α]R (3,1,-2/3)
leptons [Lα]L (1,2,-1)leptons [e]R (1,1,-2)
Higgs (Spin = 0):
H-Doublet [H0,H-] (1,2,-1)
Masses of quarks, leptons and vectorbosons by spontanous symmetry breaking
Martin zur Nedden, HU Berlin 32Physics at the LHC, Academic Training DESY Zeuthen June 2007
Motivation for Super Symmetry
Fermion ↔ Boson Symmetry
basic idea: unification of all forces, no difference between fermions (matter) and bosons (forces)
generator of the SUSY algebra: Q|boson> = |fermion> Q|fermion> = |boson>
Difference in spin = ½, doubling of the number of particles
SUSY transformation: δ|b> = ε|f> (anti-) kommutator relations {f,f} =0, [b,b] = 0,
{ε,ε} = 0 : SUSY generators are fermionic
Q has spin = ½ , may change the helicity 2-component spinor super symmetric algebra: connection of particles with different spins
Martin zur Nedden, HU Berlin 33Physics at the LHC, Academic Training DESY Zeuthen June 2007
electron
selectron
quark
squark
photon
photino
Unification ofUnification ofbosons withbosons with fermionsfermions
forces withforces with mattermatter
fermiosfermios
bosonsbosons
bosonsbosons
fermionsfermions
Super symmetric Partners
Martin zur Nedden, HU Berlin 34Physics at the LHC, Academic Training DESY Zeuthen June 2007
Minimal Super Symmetric Model (MSSM)
Most simple case: N=1 generators 2 super multiplets:
NDoF (bosons) = NDoF(fermions)
1. chiral super multiplet [Φ , Ψ] (spin 0, ½), fermions: 2 scalars,
Weyl-spinor with helicity, L/R
2. vector multiplet [λ , A] (spin ½, 1), bosons: gauge boson,
massless spin ½ fermion
● each fundamental particle has to occur in a super multiplet
● each SM particle has a SUSY-partner, Δs = ½ (minimal number of new particles)
● fermions in the vector multiplet transforms like gauge bosons (same for L/R)
● chiral multiplet contains all fermions, also with different transformation behaviour
● unbroken super symmetry: all masses were the same obviously not the case……
SUSY must be (weakly) broken, big masses of super symmetric partners
● More than 100 new parameters for the theory !?
Martin zur Nedden, HU Berlin 35Physics at the LHC, Academic Training DESY Zeuthen June 2007
Extended Higgs Model in MSSM
tand
u
H
H
22'2
222
)174(2
GeVgg
MHH Zdu
2 Higgs Dublets needed, to give all particles mass
Complex fields 8 degrees of freedom 3 absorbed in the longitudinal components of W- and Z-bosons 5 higgs bosons remains, 3 are neutral
h0 : light Higgs, scalar H0 : heavy Higgs, scalar A0 : neutral Higgs, pseudo-scalar, PC-odd H+/H- : charged Higgs, scalar
h0/H0 mixing states of Re(Hu
0) and Re(Hd0),
Mixing angle α
A0 mixing state ofRe(Hu
0) and Re(Hd0),
Mixing angle tanβ
H+/H- mixing state ofHu
+ and Hd-,
Mixing angle tanβ
222AWHmMm 2cos4
2
1 22222222, ZAZAZAhH MmMmMmm
new parameter
For the masses follows:
Martin zur Nedden, HU Berlin 36Physics at the LHC, Academic Training DESY Zeuthen June 2007
Higgs Masses in MSSM
● Higgs masses depends on 2 parameters: tan β and mA :
– tan β 1 : mh = 0 , mH2 = MZ
2 + mA2
– tan β ∞: mh = min(MZ, mA), mH = max(MZ,mA)
– Mass terms for A0, H0 and H+/H- could be very big!
– If mA big: mA ~ mH ~ m H+/-
– Mass of h0 is limited: 0 < mh < |cos2β|MZ
mh < mA < mH
mH > MZ, m H+/- > MW
– Radiative corrections important for mh (enlarges the mass)
– mh0 < 150 GeV upper limit for MSSM
– mh0 < 190 GeV limit for SUSY
Martin zur Nedden, HU Berlin 37Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSSM Higgs Masses
All Higgs masses are fixed relative to 2 parameters:
Martin zur Nedden, HU Berlin 38Physics at the LHC, Academic Training DESY Zeuthen June 2007
Cancelation of Quantum corrections in SUSY Models
Martin zur Nedden, HU Berlin 39Physics at the LHC, Academic Training DESY Zeuthen June 2007
Supersymmetric Particles
Chargino :
(partner of W)
Neutralino :
(partner of Z, g)
Smuon :
(partner of muon)
Martin zur Nedden, HU Berlin 40Physics at the LHC, Academic Training DESY Zeuthen June 2007
Super Partners
● qL, qR, lL, lR squarks, sleptons (spin = 0)
● Gauge bosons g, W, B (gluino, Wino, Bino) = gauginos
● SM: coupling of W0/B0 to Z0/γ Zino, Photino
● Higgs (scalar) 2 Higgsinos (chiral super multiplet)
● chiral super multiplet: left handed particles only
● gauge interaction the same for squarks/sleptons and quarks/leptons
● unification with gravity: Graviton Gravitino
● neutral fermionic partners Wino/Bino have the same quantum numbers as the super symmetric Higgs partners: mixing to 4 neutralinos χ0
i (i=1..4) :
the lightest neutralino is the LSP (if R-parity is conserved)
● charged Higgsinos: mixing to charginos χ+/-j, (j=1,2)
Martin zur Nedden, HU Berlin 41Physics at the LHC, Academic Training DESY Zeuthen June 2007
SUSY Interactions (R-Parity conserved)
R-parity: +1 for “normal particles, -1 for super symmetric partners
Feynman graphs:
replace at any SM-vertex(3 or 4 particle interaction)two legs by the correspondingsuper symmetric partners
The coupling constants remains the same as in SM (strong or electroweak)
Martin zur Nedden, HU Berlin 42Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSUGRA - Parameters
● m0 : universal scalar mass at GUT scale
● m½ : universal gaugino mass at GUT scale
● tan β : ratio of Higgs vacuum expectation value
● A0 : universal s-fermion mass mixing parameter
● sgn μ: sing of Higgsino mass parameter ● M(SUSY) < 1 TeV for LSP● important limits from LEP and TEVATRON
Martin zur Nedden, HU Berlin 43Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSUGRA Masses
Martin zur Nedden, HU Berlin 44Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSUGA Szenarios 1
Martin zur Nedden, HU Berlin 45Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSUGRA Szenarios 2
Martin zur Nedden, HU Berlin 46Physics at the LHC, Academic Training DESY Zeuthen June 2007
SUSY at Hadron-Colliders
search strategy: Big contribution from standard model QCD-background (Jets) look for high pT leptons and MET
- squarks and gluinos: MET (strong interaction)- neutralinos and charginos: MET and high pT leptons (electro weak interaction)
Martin zur Nedden, HU Berlin 47Physics at the LHC, Academic Training DESY Zeuthen June 2007
Squark und Gluino Searches at TEVATRON
production:
decay:
Search for Jets und ETmiss
Martin zur Nedden, HU Berlin 48Physics at the LHC, Academic Training DESY Zeuthen June 2007
Result: Upper Limits (exclusions limits)
Martin zur Nedden, HU Berlin 49Physics at the LHC, Academic Training DESY Zeuthen June 2007
Search for Neutralinos and Charginos
01
01
021
~~~~~ leepp
01
01
~~ le
No improved SUSY limit foundby TEVATRON up to now
Martin zur Nedden, HU Berlin 50Physics at the LHC, Academic Training DESY Zeuthen June 2007
Recostruction of SUSY Particles
Neutralino 2 Sbottom Gluino
CMS MC analysisM = 595 GeV
M = 510 GeV
M = 174 GeV
M = 150 GeV
M = 96 GeV
edge = 78.9 +/- 2.1 GeV M = 499.4 +/- 6.6 GeV M = 585.1 +/- 11.1 GeV
Martin zur Nedden, HU Berlin 51Physics at the LHC, Academic Training DESY Zeuthen June 2007
SUSY in R-Parity violating Processes
neutralino (LSP) unstable, no longer a dark matter candidate lepton / and baryon number conservation violated much more possible decay channels ….
L - violation B - violationL - violation
Martin zur Nedden, HU Berlin 52Physics at the LHC, Academic Training DESY Zeuthen June 2007
Neutralino in R-Parity violating Decays
production:
decay:
Evidence: 3 charged leptons in FS
Martin zur Nedden, HU Berlin 53Physics at the LHC, Academic Training DESY Zeuthen June 2007
Search at Tevatron (Neutralino decay)
production:
decay:
Evidence: 3 charged leptons in FS
Result from D0, TEVATRON:upper limit
Martin zur Nedden, HU Berlin 54Physics at the LHC, Academic Training DESY Zeuthen June 2007
Masse of the lightest MSSM-Higgs
Mass of the lightestHiggs as a functionof MA und tan(ß) from 1.6 to 15
Martin zur Nedden, HU Berlin 55Physics at the LHC, Academic Training DESY Zeuthen June 2007
Supersymmetric Higgs
Martin zur Nedden, HU Berlin 56Physics at the LHC, Academic Training DESY Zeuthen June 2007
Search for the neutral MSSM Higgs
Searches at TEVATON: using multi – jet events
Martin zur Nedden, HU Berlin 57Physics at the LHC, Academic Training DESY Zeuthen June 2007
Di-Jet Mass (D0 / Tevatron) MSSM Higgs
Search for overshoot in the invariant mass distribution of the two jets with the highest pT
At least 3 b-flavoured jetare requested per event
BG: multi jet production
Martin zur Nedden, HU Berlin 58Physics at the LHC, Academic Training DESY Zeuthen June 2007
Upper Limit for the MSSM-Higgs Mass
based on di-Jet events
Martin zur Nedden, HU Berlin 59Physics at the LHC, Academic Training DESY Zeuthen June 2007
Search for the MSSM charged Higgs
Search for MET + J + X:
Direct production in weak IA,compeditiv to t Wb
Martin zur Nedden, HU Berlin 60Physics at the LHC, Academic Training DESY Zeuthen June 2007
MSSM – Higgs Search at LHC
All region is coverd…
Martin zur Nedden, HU Berlin 61Physics at the LHC, Academic Training DESY Zeuthen June 2007
SUSY Mass Spectra