THE LHC/LC SYNERGY S. Dawson, BNL December, 2002 Why we need both the LC and the LHC Examples: EWSB, SUSY, top quark The cosmological connection
Feb 14, 2016
THE LHC/LC SYNERGY S. Dawson, BNL December, 2002
Why we need both the LC and the LHC Examples: EWSB, SUSY, top quark The cosmological connection
Why are we here?
• Not to compare/ contrast LHC/LC• Rather to see how physics info from one
machine can influence physics results from the other
• Goal: Working group document, Spring 03
Weiglein, Oreglia
What do we want to know?
• What is the origin of EWSB?– Is it a Higgs?– Is it something else?
• What is the origin of fermion masses?– Understanding the top quark
• Is there physics at an intermediate scale? (and what is the scale?)– Is it SUSY?– Is it little Higgs?– Is it extra dimensions?– …..
Is mass due to a Higgs boson?
• Production rates at LEP, Tevatron, LHC fixed in terms of mass
• Direct search limit from LEP
• Higgs contributions to precision measurements calculable
WWWh
fffh
gMgv
mg
clGeVM h %95@114
clGeVM h %95@196
Precision measurements:
G. Mylett, Moriond02
LHCHiggs Discovery at Tevatron or LHC
Tevatron
Carena, Conway, Haber, Hobbs, hep-ph/0010338
ATLAS TDR
Is it a Higgs?• How do we verify role in
EWSB?• Measure Yukawa couplings
• Measure spin/parity
• Reconstruct Higgs potential
2
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mm
hbbh b
0PCJ
42
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22
822h
vMh
vMhMV hhh
Higgs properties at LHC• LHC measures B
– Eg, ggh depends on ggh and h couplings– Result is combination of coupling constants
• Significant PDF uncertainties– Cancel in ratios
• Weak boson fusion depends on SU(2) assumption about WWh and ZZh couplings– Precision measurement for Mh>140 GeV from WBF
Zeppenfeld, Belyaev, Reina
Higgs Measurements at LHC
• Mh<140 GeV, H/H10-20%
• Not all channels possible
• tth, h+- critical
Belyaev & Reina, hep-ph/0205270
200 fb-1
300 fb-1 (tth,h, Wh,hbb)
Untangle Higgs Couplings
• PDF uncertainties cancel in ratios
• Improved precision by fixing bbh/h coupling to SM value
• Note lousy precision on bbh• Theory systematic error:
– 20% (ggh)– 5% (WBF)– 10% (pptth)
Belyaev & Reina, hep-ph/0205270200 fb-1
• Well determined initial state– Precision masses with
recoil technique– Higgs mass independent of
Higgs decay – Model independent Higgs
BRs
yrHiggsGeVM h
/000,40120
Zhee
22 2 ZZh MEssM
Van Kooten
Coupling Constant Measurements at LC
Battaglia & Desch,
hep-ph/0101165
LC
%21WWhg
%2bbhg
L=500 fb-1, s=350 GeV
Compare LHC:
gbbh40-50%
WBF, 600 fb-1
gbbh 10-20%
Piccinini & Polosa, hep-ph/0211170
At LC, largest uncertainty is theory from mb!
Who cares about Higgs Couplings?And how well do we need to do?
• SUSY models, gbbh enhanced at large tan , small MA …info about SUSY parameters
• Little Higgs, topcolor models, new physics in gtth
Logan
Higgs mass measurements
• LC:
• LHC:Direct reconstruction of
LC @ 350 Gev
Conway, hep-ph/0203206
MeVMfbGeVM
h
h
50500,120 1
h
MeVMfbGeVM
h
h
100300,150 1
Primarily interesting for comparison with precision EW measurements
• Angular correlations of decay products distinguish scalar/pseudoscalar
Miller, hep-ph/0102023
Threshold behavior measures spin
[20 fb-1 /point]
Higgs spin/parity in e+e-Zh
Higgs self couplings difficult at LHC
Baur, Plehn, Rainwater, hep-ph/021124
gghhW+W-W+W-(jjl)(jjl) ghhh=Mh2/2v
Measuring Higgs Self Couplings at LC• Must measure e+e- Zhh
• Small rate .2 fb for Mh=120 GeV
large background
• Large effects in SUSY– Resonances– ghhh suppressed MA < 300 GeV
%24
1000 1
hhh
hhh
fb
Lafaye, hep-ph/0002238
Castanier, Gay, Lutz, Orloff, hep-ph/0101028
Is the world Supersymmetric?
Find SUSY particles
Find SUSY partners
Check impact on precision measurements
Measure SUSY couplings
Reconstruct underlying GUT theory
Light SUSY consistent with Precision Measurements
• SUSY predicts light Higgs, Mh<130 GeV
• For MA, SUSY Higgs sector looks like SM• Can we tell them apart?• Higgs BR are different in SUSY• Find all SUSY Higgs HAHh ,,, 000
LHC
Find all the Higgs Bosons
Carena, hep ph/9907422
Tevatron
collider sensitive
Gunion 4 years at !
Into the wedge
• e+e- H+H-, H0A0
Observable to MH=460 GeV
at s=1 TeV• e+e- H+,H+tb L=1000 fb-1, s=500 GeV, 3 signal for MH 250 GeV• e+e- W+H-
Largest at low tan s=500 GeV, .01 fb
Moretti, hep-ph/0209210Logan & Su, hep-ph/0206135
mSUGRA simplest version of SUSY• 4 parameters, 1 sign
– m0 (scalar mass at MGUT)– m1/2 (gaugino mass at MGUT)– A0 (mixing term)– tan (ratio of Higgs VEVs)
Measure m(gluino) at LHC predict m(neutralino) at LC
2/1~2/1~2/1~ 5.2,4.,8.1
01
mmmmmm g
Very predictive…all masses and couplings predicted
Relationships are different for GMSB, AMSB…..
•LHC/Tevatron will find SUSY• SUSY mass differences
from cascade decays;eg
• M0 limits extraction of other masses
• Fit to SUGRA parameters
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Catania, CMS
Baer
LC makes precision mass measurements
• Chargino pair production, S-wave
• Rises steeply near threshold• This example:
Blair, hep-ph/99910416
%1.mm
How do we distinguish a chargino from a 4th generation lepton?
Feng, hep-ph/0210390
LC mass measurements from endpoint spectra
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LC can step through Energy Thresholds Run-time Scenario for L=1000 fb-1
Year 1 2 4 5 6 7
L (fb-1) 10 40 150 200 250 250
• SUSY masses to .2-.5 GeV from sparticle threshold scans M0/M0 7% (Combine with LHC data)• 445 fb-1 at s=450-500 GeV• 180 fb-1 at s=320-350 GeV (Optimal for Higgs BRs)• Higgs mass and couplings measured, gbbh1.5%
• Top mass and width measured, Mt150 GeV
Battaglia, hep-ph/0201177
LHC: Fits to SUSY Parameters
Bachacou, Hinchliffe, Paige, hep-ph/9907518
LC accuracy
LHC: Mass reconstruction limited by LSP mass
LHC sensitive to mass
differences
Measurement of LSP massat LC improves LHC
mass resolution
SUSY: LC+LHC• LHC sensitive to
heavy squarks• Use neutralino
mass, couplings from LC
• CMS study:10 fb-1 gives squark, gluino masses to 1-2% if neutralino mass known from LC
R. Van Kooten: “Bands, not blobs”
Combine LC/LHC mass measurementsWindow to high scales?
• LC measures chargino, neutralino, selectron masses from thresholds
• LC extracts mixing parameters from cross section measurements
• LHC measures gluino, squark masses
• RGE evolve parameters to GUT scale
Sample mass measurements (SPS#1A):LC:
LHC:
%2.1.~~ 012,1
%21~~~, gue LRR
Do gaugino & Scalar masses unify in mSugra?
Freitas, hep-ph/0211076
Gaugino masses Scalar masses
SUSY Couplings:• Compare rates at NLO:
• Lowest order,
• Super-oblique corrections sensitive to higher scales
•
• Masses from endpoints
• Assume
• Tests coupling to 1% with 20 fb-1
XffffX gg ~~
gqqee
gqqee
gqqee
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~~
ss gg ~
mmg
gg s
s
s~
ln16
~~~ 2
2
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Bee ~~
eeB~~
Feng
Probes mechanism of SUSY breaking
Are we being too simplistic?
• Many possibilities beyond MSSM• Suppose explicit CP violation
– Complex tri-linear mixing• Instead of h,H, and A
3 states which mix• Holes in LEP limits on Higgs search• New phenomenology Carena, Mrenna
Cosmic Connections• LC/LHC can give
insight into origin of dark matter
• SUSY provides dark matter candidate, LSP
• LSP is weakly interacting, neutral and stable
• mSUGRA predicts everything in terms of 5 parameters
• Calculate 0 relic density
• Assume 2 around central value
.07 <Xh2<.21
Requires m1/2>300-400 GeVM(+
)>240 GeVM(o)>120 GeV
Arnowitt and Dutta, hep-ph/0204187
Assume Dark Matter is 0
Forbidden by 3 g-2
Dark Matter at large tan
• CLEO bound from bs
• Similar allowed region from dark matter
• Does this picture persist for more complicated SUSY models?
1.8 x 10-4<B(bs) <4.5 x 10-4
Understanding the Top Quark
• Why is Mt v/2 ?• Kinematic reconstruction
of tt threshold gives pole mass at LC
• Compare LHC
MeVMfb
t 20040 1
Groote , Yakovlov, hep-ph/0012237
QCD effects well understood
NNLO ~20% scale uncertaintyGeVMfb
t 2150 1
2Mt (GeV)
Who cares about precision Mt?
• Precision Mt, MW test consistency of SM
• Limits Higgs mass, SUSY parameters
Top Yukawa coupling tests models
• tth coupling sensitive to strong dynamics
• Above tth threshold e+etth• Theoretically clean s=700 GeV, L=1000 fb-1
• Large scale dependence in tth rate at LHC
• L=300 fb-1
%5.6tth
tth
gg
Baer, Dawson, Reina, hep-ph/9906419
Juste, Merino, hep-ph/9910301
Reina, Dawson, Orr, Wackeroth, hep-ph/0211438
Beenacker, hep-ph/0107081
% 16 tth
tth
gg
tth at LC
• 20 % measurement of gtth to mh=200 GeV using hWW decay
• Needs s=800 GeV
Gay, 02
What if the LHC doesn’t find a Higgs????
• Still have to understand MW, precision measurements• Fit to S, T0
Without Higgs, effective theory
• For new physics at 3 TeV scale, EW fits give a,b1
• Models which satisfy EW constraints without Higgs tend to have new Z’ or light t’s
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Bagger, Falk, & Schwartz, hep-ph/9908327
Hill & Simmons, hep-ph/0203079
Exciting physics ahead
• LHC/Tevatron finds Higgs LC makes precision measurements of couplings to determine underlying model• LHC finds evidence for SUSY, measures mass differences LC untangles spectrum, finds sleptons LHC/LC combination makes precision measurements of couplings and masses;
Untangles GUT theory