academic training, part 4: higgs search and beyond ... · exists due to the massive gauge field w,z...

Martin zur Nedden , HU Berlin 1Phy sics at the LHC, Academic Training DESY Zeuthen June 2007

Phy s ics at the LHC

Academ ic Training, Part 4 :Higgs Search and Bey ond Standard Model

Dr. Sv en Moch, DESY Zeuthen (Theory )

Dr. Martin z ur Nedden, HU Berlin (Experiment)

June 2007 DESY Zeuthen, bas ed on a lecture in WS 06 / 07 at Humboldt Univ ers ity Berlin


Plan

● LHC: Experimental Ov erv iew and

Standard Model Phy s ics (Part 3)– Monday , June 11 , 2007, 9 .00 - 10 .30

● LHC: Higgs Searches and

Phy s ics bey on the Standard Model (Part 4 )– Thursday , June 14 , 2007, 10 .00 – 11 .30


Contents

● Discov eries at the energy frontier● Ov erv iew : LHC and its experiments● Hadron- Hadron interactions● Jets : fragmentation, s ignature and algorithms● Standard model channels at LHC● top- phy s ics and heav y flav or recons truction● Higgs : ev ent topologies and search s trategies● SUSY: searches in the MSSM


Higgs Searches

● Yukav a- coupling, masses of fermions

● experimental ev idence:– production– decay s and s earch channels

● results from TEVATRON● searches at LHC


Higgs Mechanism in the Standard Model

• Doublet of scalar Higgs fie lds H(x) exists due to the m assive gauge field W,Z and the m assless

• Complex fie lds + , 0 → 4 real com ponents 1, … 4, p roduce m ass in sym m etry breaking due to self- in teract ion

• Golds tone/ Higgs - mechanism : 3 com ponents absorbed in the

longitud inal polariz at ion of the m assive 3 Wi- bosons

• 1 phy s ical s tate H remains • coupling to mas s w ith g ffH

• No pred ict ion of Higgs m ass by SM

( )00

2

1 Φ−Φ=H

HgHff

ΨΨ


Yukav a coupling, Mass of Fermions

[ ] [ ] ),,( 00

L

eRRLe e

eeeGL

ΦΦ+

ΦΦ−∝ −

+ νυ

( ) ( ) )(22)(

0

2

1xheeee

Geeeev

GL

xhv LRRLe

LRRLe +−+−∝⇒

+

=Φ

)(2

xheev

meemL

vGm e

ee

e −−∝⇒≡

ΨΨmnew term in Lagrangien needed: excluded due to gauge inv ariance

e R(T= 0, Y= - 2)

e L(T= 1/ 2 , Y= - 1)

h 0 (T= 1 / 2 , Y= 1)

igm e/ (2MW)igMW

W

W

(Single t in I,Y)

choos e :

Coupling to the higgs fie ld

h0


Consequences from Yukav a- Coupling

● elect ron gets m ass● n eu t r in o res t m ass les● s t ren gth of cou p lin g p rop or t ion al to th e m ass

of th e ferm ion● m ass is n ot p red icted by th e th eory● m asses for qu arks :

– sam e form alism as for lep tons

– difference: both quarks with in the doublet have m ass

● new Higgs Doublet c


Higgs - Production in Hadron- Hadron Interactions

gluon- gluon interaction (LHC/ TEVATRON):big production cros s s ection,decay in 2 gam m as

gluon- gluon interaction (LHC/ TEVATRON):production cros s s ection v ery s m all

quark- antiquark interaction (TEVATRON):big production cros s s ection at 2TeV (TEVATRON)decay : W,Z → leptons

quark- quark interaction (LHC):big production cros s s ection at 14TeV (LHC)decay : W,Z → 2 (or leptons )


Decay Width of Different Higgs Channes l

2

3

2

22

)4

1(24

)(H

fHfFc M

mMmGNffH −=→Γ

π

)124

1()41(28

)( 4

4

2

221

2

23

H

W

H

W

H

WHF

M

M

M

M

M

MMGWWH +−−=→Γ −+

π

)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 +−−=→Γ

π

2

2

2

2

22

3

32

)()(32128

)(H

WW

H

qqq

q

HF

M

MI

M

mIe

MGH +Σ=→Γ

παγγ

Calculations in the s tandard m ode l:


Higgs – Decay Channels

Γ(H → VV) ~ GF M3

H

Γ(H → ) ~ 2 GF M3H

Γ(H → ff) ~ GF m 2f MH


Poss ible Higgs Decay s / coupling cons tants

ffH →0

−+→ WWH 0

γγ/0 ggH →

WW

f

Hff M

emg

ϑsin2=

W

WWWH

eMg

ϑsin=

WW

ZZZH

eMg

ϑϑ cossin=

22

1

2

2

)2(228 WFWWHF

W

MGgG

M

g =⇒=


Higgs Search Strategies

bbHZpp νν→→ *

Good channe l for TEVATRON:

M(H) > 135 GeV: H → WWM(H) < 135 GeV: H → bb

gg- fus ion dom inant at all Higgs m as s es , not to s eparate from BG at M < 135 GeV

qq: Higgs - Strahlung: s m all contribution, but god to s eparate from BG


Cross Sections at TEVATRON


Higgs Search at TEVATRON, upper Limit

s ignal: 2 b- Je t + MET + 2 leptons

if M(H) > 135 GeV


Upper Limit for Higgs production at TEVATRON

if M(H) < 135 GeV


Higgs Decay Channels : Branching Ratios


Higgs Decay in the Standard Modell

fermions

bosons

decay w idth branching ratio


Higgs Cross Sections at LHC

gluon- gluon fus ion

v ector bos on fus ion


Higgs : Signal to background ratio at LHC

for M(Higgs ) = 150 GeV:

S/ B < 10 - 10


Higgs to 2 Z and 4 Leptons

CMS TDR

Very clean an good measurabe ev ent s ignature:4 high pT leptons , 2 inv ariant masses at MZ


Gluon- Gluon Fus ion to 4 Leptonen (Atlas / LHC)

Atlas TDR

inv ariant masse (ZZ → 4 l)

Background , not tod is t ingu ish from Higgs- Signal:qq → ZZ → 4 leptons


Higgs to 2 Gamma

CMS

also v ery clean s ignature, but small cross section:2 high pT isolated EMC- clus ters


Gluon/ Gluon Fus ion to 2 Gamma (Atlas / LHC)

ATLAS TDR

Background:Not reducable : pp → XReducable : pp → J J


Vektor- Boson Fus ion: Decay to 2 W- Bosons

H→ WW→ eµ

Atlas TDRH→ WW → l l (l qq )

Signature:Je ts + 2 high pT leptons + MET

No m as s peak (MET from neutrino), calculate the trans v ers e m as s

Background:tt, Wt, WWJJ production


Higgs to 2 Tau

H → → e µ:

H → → l l + 4 (l + J + 3 )

Atlas TDR

2 high pT leptons , big MET

Mass reconstruction poss ible, ev en w ith high MET

Background:Zjj , tt


Higgs Discov ery potential of LHC/ ATLAS

Dependency on Higgs mass and decay channel


Discov ery potential of ATLAS/ LHC

Dependency of Higgs - mass and Luminos ity


SUper SYm m etry

● “Beyon d th e Stan d ar t Mod el”● in t rod u ct ion in to SUp er SYm m etry● Min im al Su p er Sym m etr ic exten s ion of

th e s tan d ard Mod el (MSSM)● su p er sym m etr ic in teract ion s● SUSY breakin g● p ar t icle sp ect ra of SUSY

(p h en om en ology)● SUSY search es


Global Fit of Standard Model Parameter


Weinberg Angle and Higgs - Masse


Standard Model Sy mmetry

• SM describes strong and electroweak interact ions, L/ R asymmetry

• Based on symmetries and gauge invariance• All forces p ropagated by exchange of gauge fields (local gauge

fields)YLC USUSU )1()2()3( ⊗⊗Gauge- Bos ons (Spin = 1 ):

glu on s Ga SU(3) (8 ,1 ,0)

vector boson s Wi SU(2) (1 ,3 ,0)

abelian boson B U(1) (1 ,1 ,0)

Ferm ions Spin = ½ :

qu arks [Ui ,Di ]L (3 ,2 ,1 / 3)qu arks [Ui ]R (3 ,1 ,4 / 3)qu arks [Di ]R (3 ,1 ,- 2/ 3)

lep ton s [L ]L (1 ,2 ,- 1)lep ton s [e]R (1 ,1 ,- 2)

Higgs (Spin = 0 ):

H- Dou blet [H0,H- ] (1 ,2 ,- 1)

Mas s es of quarks , leptons and v ectorbos ons by s pontanous s y m m etry breaking


Motiv ation for Super Sy mmetry

Fermion ↔ Boson Sy mmetry

bas ic idea: unification of all forces , no difference be tw een ferm ions (m atter) and bos ons (forces )

generator o f the SUSY algebra: Q| bos on> = | ferm ion> Q| ferm ion> = | bos on>

Difference in s pin = ½ , doubling of the num ber o f particle s

SUSY trans form ation: | b> = | f> (anti- ) kom m utator re lations {f,f} = 0, [b,b] = 0 , →{ , } = 0 : SUSY generators are fermionic

Q has s pin = ½ , m ay change the he licity → 2 - com ponent s pinor s uper s y m m etric algebra: connection of particle s w ith different s pins


electron

selectron

quark

squark

photon

photino

Unification ofUnification ofbosons withbosons with fermionsfermions

forces withforces with mattermatter

fermiosfermios

bosonsbosons

bosonsbosons

fermionsfermions

Super sy mmetric Partners


Minimal Super Sy mmetric Model (MSSM)

Most s im p le case: N= 1 generators 2 s uper m ultiple ts :

NDoF (bosons) = NDoF(fermions)

1 . chiral s uper m ultiple t [ , ] (sp in 0 , ½), ferm ions : 2 scalars ,

Weyl- sp in or with h elicity, L/ R

2 . v ector m ultiple t [ , A] (sp in ½, 1), bos ons : gau ge boson ,

m ass less sp in ½ ferm ion

● each fu n d am en tal p ar t icle h as to occu r in a su p er m u lt ip let

● each SM p art icle h as a SUSY- p artn er , s = ½ (m inim al num ber of new particle s )

● ferm ion s in th e v ector m ultiple t t ran s form s like gau ge boson s (sam e for L/ R)

● chiral m ultiple t con tain s all ferm ion s , a lso with d ifferen t t ran s form at ion beh aviou r

● u n broken su p er sym m etry: all m as s es w ere the s am e obv ious ly not the cas e……

SUSY m us t be (w eakly ) broken, big m as s es of s uper s y m m etric partners

● More than 100 new parameters for the theory !?


Extended Higgs Model in MSSM

βtan=d

u

H

H

22'2

222

)174(2

GeVgg

MHH Z

du =+

=+

2 Higgs Duble ts needed, to giv e all particle s m as s

Com p lex field s → 8 d egrees of freed om 3 abs orbed in th e lon gitu d in al com p on en ts of W- an d Z- boson s → 5 higgs bos ons rem ains , 3 are n eu t ral h 0 : light Higgs , s calar H0 : heav y Higgs , s calar A0 : neutral Higgs , ps eudo- s calar, PC- odd H+ / H- : charged Higgs , s calar

h 0/ H0 m ix ing s tates o f Re(Hu

0) and Re(Hd0),

Mixing angle

A0 m ixing s tate o fRe(Hu

0) and Re(Hd0),

Mixing angle tan

H+ / H- m ix ing s tate o fHu

+ and Hd- ,

Mixing angle tan

222AWH

mMm +=± ( ) ( ) β2cos421 22222222

, ZAZAZAhH MmMmMmm −+±+=

new param eter

For the m as s es fo llow s :


Higgs Masses in MSSM

● Higgs masses depends on 2 parameters: tan and m A :

– tan → 1 : m h = 0 , m H2 = MZ

2 + m A2

– tan → ∞ : m h = min(MZ, m A), m H = max(MZ,m A)

– Mass terms for A0, H0 and H+ / H- could be very big!

– If m A big: m A ~ m H ~ m H+ / -

– Mass of h 0 is limited : 0 < m h < | cos2 | MZ

m h < m A < m H

m H > MZ, m H+ / - > MW

– Radiat ive corrections important for mh (enlarges the mass)

– m h0 < 150 GeV upper limit for MSSM

– m h0 < 190 GeV limit for SUSY


MSSM Higgs Masses

All Higgs m as s es are fixed re lativ e to 2 param eters :


Cancelation of Quantum corrections in SUSY Models


Supersy mmetric Particles

Chargino :

(p ar tn er of W)

Neutralino :

(p ar tn er of Z, g)

Sm uon :

(p ar tn er of m u on )


Super Partners

● qL, qR, lL, lR → squarks , s leptons (sp in = 0)

● Gauge bosons g, W, B → (gluino , Wino , Bino) = gauginos

● SM: coupling of W0/ B0 to Z0/ → Zino , Photino

● Higgs (scalar) → 2 Higgs inos (chiral super multip let)

● chiral super multip let: left handed part icles only

● gauge interact ion the same for squarks/ slep tons and quarks/ lep tons

● unification with gravity: Grav iton → Grav itino

● neutral fermionic partners Wino/ Bino have the same quantum numbers as the super symmetric Higgs partners: m ixing to 4 neutra linos 0

i (i= 1 ..4 ) : the lightest neutralino is the LSP (if R- parity is conserved)

● charged Higgs inos : m ixing to charginos + / -j, (j= 1 ,2 )


SUSY Interactions (R- Parity conserv ed)

R- p ar ity: + 1 for “n orm al p ar t icles , - 1 for su p er sym m etr ic p ar tn ers

Fey nm an graphs :

replace at any SM- v ertex(3 or 4 particle interaction)tw o legs by the corres pondings uper s y m m etric partners

Th e cou p lin g con s tan t s rem ain s th e sam e as in SM (s t ron g or elect roweak)


MSUGRA - Parameters

● m 0 : u n iversal scalar m ass at GUT scale

● m ½ : u n iversal gau gin o m ass at GUT scale

● t an : rat io of Higgs vacu u m exp ectat ion valu e

● A0 : u n iversal s - ferm ion m ass m ixin g p aram eter

● sgn : s in g of Higgs in o m ass p aram eter ● M(SUSY) < 1 TeV for LSP● im p ortan t lim its from LEP an d TEVATRON


MSUGRA Masses


MSUGA Sz enarios 1


MSUGRA Sz enarios 2


SUSY at Hadron- Colliders

search s trategy :→ Big contribution from s tandard model QCD- background (Jets )→ look for high pT leptons and MET

- squarks and gluinos : MET (s trong interaction)- neutralinos and charginos : MET and high pT leptons (e lectro w eak interaction)


Squark und Gluino Searches at TEVATRON

production:

decay :

Search for Jets und ETm is s


Result: Upper Limits (exclus ions limits )


Search for Neutralinos and Charginos

01

01

021

~~~~~ χχυχχ leepp →→ ±

01

01

~~ χχµυle→

No im prov ed SUSY lim it foundby TEVATRON up to now


Recos truction of SUSY Particles

Neutralino 2 Sbottom Gluino

CMS MC analy s isM = 595 GeV

M = 510 GeV

M = 174 GeV

M = 150 GeV

M = 96 GeV

edge = 7 8 .9 + / - 2 .1 GeV M = 49 9 .4 + / - 6 .6 GeV M = 585 .1 + / - 1 1 .1 GeV


SUSY in R- Parity v iolating Processes

→ neutralino (LSP) uns table, no longer a dark matter candidate→ lepton / and bary on number conserv ation v iolated→ much more poss ible decay channels ….

L - v iolation B - v iolationL - v iolation


Neutralino in R- Parity v iolating Decay s

production:

decay :

Ev idence: 3 charged leptons in FS


Search at Tev atron (Neutralino decay )

production:

decay :

Ev idence: 3 charged leptons in FS

Result from D0, TEVATRON:upper limit


Masse of the lightes t MSSM- Higgs

Mas s o f the lightes tHiggs as a functionof MA und tan(ß ) from 1 .6 to 15


Supersy mmetric Higgs


Search for the neutral MSSM Higgs

Searches at TEVATON: us ing multi – jet ev ents


Di- Jet Mass (D0 / Tev atron) MSSM Higgs

Search for ov ershoot in the inv ariant mass dis tribution of the tw o jets w ith the highes t pT

At leas t 3 b- flav oured jetare reques ted per ev ent

BG: m ulti je t production


Upper Limit for the MSSM- Higgs Mass

bas ed on di- Jet ev ents


Search for the MSSM charged Higgs

Search for MET + J + X:

Direct production in w eak IA,com peditiv to t → Wb


MSSM – Higgs Search at LHC

All region is cov erd…


SUSY Mass Spectra

academic training, part 4: higgs search and beyond ... · exists due to the massive gauge field w,z...

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