Emmanuelle PEREZ CEA-Saclay, DSM / DAPNIA / Spp

1

Emmanuelle PEREZCEA-Saclay, DSM / DAPNIA / Spp

Rencontres du VietNam, Hanoi 10 August 2004

5th Rencontres du VietNam – New Views in Particle PhysicsHanoi, 5-11 August 2004

Searches for New Phenomena :Where do we stand …

and what we might learn within the coming years …

Rencontres du VietNam, 08/042 E. Perez

Searches for New Physics : why, where, how…

Mechanism of the EW symmetry breaking ?

Higgs (i.e. fundamental scalar) ? Find it… structure of the Higgs sector ? solution of the hierarchy problem ?

no Higgs ? Dynamical breaking ? ( H ~ condensate )

extra-dim physics ? ( H ~ Gauge Field|4d )

In most scenarios, new physics is expected at the TeV scale. Also hoped for, that NP might answer some of the questions unexplained by the SM.

Various strategies to track new physics, e.g. : - high precision measurements ( need good theoretical control ) - rare decays (K & B) , LFV processes - searches for Dark Matter - searches at high energy colliders Tevatron, HERA

- model driven searches- exploit at best the experimental knowledge of our detectors

Some complementarities between these different approaches.

#doublets, triplets ? CP ?

SUSY MPl ? “Little Higgs” 10 TeV ?

extra dimensions no hierarchy ?


Good performances of our facilities !

pp, s = 1.96 TeV CDF & D0

Run I (92-96) : 110 pb-1 / expRestart in may 2001 0.6 fb-1 delivered

2002

2003

2004

HERA-II

Tevatron_

HERA ep, s = 320 GeVH1 & ZEUS

until summer 2000 : 120 pb-1 / exp

restart (fall 01)Tevatron Run II

1032 cm2 s-1

threshold brokenon July 16th !

1032 cm2 s-1

threshold brokenon July 16th !

1032 cm2s-1

2.1031

6.1031Peak lumiPeak lumi average

Jan

04

Jan

03

Jan

02Serious background problems at the

Required time,

now solved

HERA isnow operating

with twicethe 2000 peak lumi

HERA isnow operating

with twicethe 2000 peak lumi

HERA-II analyses : up to 50 pb-1

+ LEP data ! Very relevant constraints on NP ! some final combinations are still to come

NB: expect several new results in the coming weeks ! some with up to 350 pb-1 !

(e+ p)

Analyses presented here 200 pb-1 of Run II data (2002 & 2003)

4

Hunting the SM Higgs Boson(LEP EW WG, April 2004)

• Status :

Direct searches at LEP MH > 114.4 GeV @ 95% C.L.

EW fits ( latest Mtop = 178.0 4.3 GeV) : MH < 237 GeVLEP final combination for MSSM Higgs coming soon…

LEP is finalizing investigations of non-standardscenarios (invisible h, bosophilic Higgs, CP-violation…)

• Until the start-up of (physics at) LHC, Higgs searches are in the hands of the Tevatron experiments :

H WW

(

pb

)

H bb

MH (GeV)

“Light” Higgs, M < 130 GeV :

• Best S/B in leptonic W/Z decays• Large bckgd from W/Z + jets b tagging !• Importance of a good mass resolution !

“Heavy” Higgs, M > 130 GeV :

Clean dilepton + ET,miss signature

(new Mtop required new databases with , BR etc…)

H bb

H WW(*)

E. Perez

a few 10-1 pb

gg H

HW


Tevatron Searches for a light SM Higgs

WH bbl with l = e,First analyses exist !

(WH) x BR < 5 pb

for MH = 115 GeV

CDF Run II Prelim., 162 pb-1

Still a factor ~ 50 largerthan SM predictions !

Exploit kinematics andtopology, require1 (2) b-tag in D0 (CDF)

SM prediction

Obs. limit

Exp. limit

Fermilab-Pub-03/320-EUpdated sensitivity study

- Full GEANT simulation, 396 ns, RunIIb Si.- experience from current data (bckgd, (Mbb) )(impact of cancellation of Si. upgrades still to be assessed)

05 06 07 08 09

10

5 4.4

8.5

End 2008 :between 4 & 8 fb-1

Inte

gra

ted L

um

i (f

b-1

) Challenging anyway !

CombiningWH & ZH,D0 & CDF

conservative(reasonably)

optimist

ic4.4 fb-1

8.5

No “golden” channel …

(also T WT lbb)


Tevatron Searches for a Heavy SM Higgs

Final states investigated : ee + ET,miss, e + ET,miss, + ET,miss

(combined ll + ET,miss in the CDF analysis)

Backgrounds from W + jet(s), Z/DY, WW

Exploit spin correlations : leptons small

e

x-section enhancedw.r.t. SM via heavy4th generation quarksin the ggH loop

No excess w.r.t. SM predictions…

(H) x BR(H WW) < 5.6 pb

for MH = 160 GeV

Will soon be sensitive …

i.e. a factor ~ 20 larger than SM predictions

SM Higgs : need ~ 4 fb-1 for sensitivity @ 95% CL

L 160 – 200 pb-1

Higgs = condensate RtL

E. Perez

( H WW* )


SUSY & Non standard Higgses

• Higgs in SUSY models : extended Higgs sector h, H, A, H

Two free parameters, e.g. MA and tan = vu/vd- Often : one Higgs looks like HSM

- Else : low (W+Higgs) but (Higgs+bb) enhanced at large tan 4b !- Difficult cases : SM = H heavy, or bb

look for A , use partially reco’ed mass

MSSM constraints Mh < 135 GeV

95% CL sensitivity over the allowed M range

CDF Run II240 pb-1

e/ + had.

For tan = 30,sensitivity still a factor ~ 10 away from MSSM

• Doubly charged Higgses :D0, hep-ex/0404015CDF, hep-ex/0406073

H++ appear in e.g. L- R symmetric models : SU(2)L x SU(2)R broken by Higgs triplet(or extended Higgs sector by a triplet with Y=2).Might explain small (Majorana) masses.

H++ couples to fermions via unknown Yukawa couplings, not related

to masses. SUSY L–R models predict low H++ masses, below 1 TeV

Search for (high mass) same-sign dileptons

Evidence of 0 at the Heidelberg-Moscow experiment ?

113 GeV

136 GeV

(CDF also searched for quasi-stable H++ , M > 134 GeV)

_

_


H++ and the HERA multilepton events

H1, EPJ C31 (2003) 17

Events with 2 leptons in final state. Mainly produced via

(different angular ranges in both

analyses)

obs. / exp.

H1 data 94-00 : excess of 2e+3e events at

high M12 = mass of two highest PT e No such excessseen in ZEUSdata

H1 analysis extended to include 45 pb-1 of 03-04 data

Extended to other 2l & 3l topologies :ee, , e, eee, e, ee

• no new 2e / 3e evt at M12 > 100 GeV

(but one high mass 3e event …)• one e event at M > 100 GeV

H1 Prelim., HERA I+II

163 pb-1

2l + 3l Altogether, at PT > 100 GeV :

Nobs = 4, Nexp = 0.61 0.11

3 / 0.23 0.043e, M12 > 100 GeV

3 / 0.30 0.042e, M12 > 100 GeV

H1 ( 115 pb-1)selectionexpt The H1 evts

are notconsistent with

e H++ (e) ee(e)

H1 94-00 data

e

E. Perez


Hunting Supersymmetry…For the last 20 years, SUSY has been “the standard non-standard theory”…

- Provides a technical solution for the “hierarchy” problem- The only symmetry which prevents to add a mass term m2 H+H- Unification of couplings : works well with SM + SUSY- Possibly provides an additional source of CP

Different models and phenomenology depending on : - the SUSY breaking mechanism (gravity mediated, or gauge interactions, anomalies ?)

- whether or not the LSP (Lightest Supersymmetric Particle) is stable

All sparticles (but the gluino) democratically produced.Strong bounds on constrained models.

Production of squarks & gluinosdominates – but large bckgdCleaner signatures from production (e.g. multileptons) but smaller cross-sections

Most relevant process is the RpV resonant production of a squark

Typical signatures with ET,miss , or , or large multiplicities or etc…

LEP Tevatron HERA

Mass bounds 100 GeVNB: no model independentbound on the LSP mass SUSY might also manifest itself in precision measurements,

rare decays, Dark Matter searches etc…


SUSY : GMSB at the TevatronGauge Mediated SUSY Breaking : - naturally avoids large unwanted FCNC - revival of interest in GMSB following “the” CDF Run I event NB : LEP analyses made the GMSB interpretation unlikely - LSP = gravitino G ( < keV), pheno. depends on NSLP

When NLSP = Neutralino : 01 G

Inclusive search for + ET,miss – might come from 02 1 production

(no spectacular eeET,miss event observed so far in Run II data)Large instrumental background (jets faking a ), determined from the data.

NB : Tevatron will provide very relevant data for the jet 0 fragmentation… cf H @ LHC !!

Interpretation withina “minimal” GMSBmodel :

M(01) > 105 GeV

M(1) > 192 GeV

M(01) > 105 GeV

M(1) > 192 GeV

185 pb-1

(D0 Prelim, 185 pb-1)

Similar results from CDF

World best limit !

(10-6 expected !)

Run I

01 mass (GeV)

~

~

E. Perez

Rencontres du VietNam, 08/0411

SUGRA-like SUSY at the Tevatron

• Pair production of q / g

large , Signature jets + ET,miss

LSP usually the 01. RPC ET,miss

~ ~

Z () + jets

Large bckgd from multijet prod. !

search domain

D0 Run II, Prelim., 85 pb-1

Interpretation within mSUGRA:

q > 292 GeV,g > 333 GeV

~~

(for some values of parameters)

Better than in Run I… but still stronger LEPbounds in this very constrained model !(roughly, g, sleptons + squarks )

~

• Chargino + Neutralino production ( 02 1 )

trilepton final states Low x BR but clean signatures

eel + el + l +same-sign

D0 Prelim., 147 – 250 pb-1

Getting close to the unexplored mSUGRA region !

Need high L and combined analyses

NB : importance of id. at large tan

D0 : pair production of squarks, q q 01

~

CDF : light sbottom squarks (156 pb-1)

g pair production, g bb1

~ ~ ~

E. Perez


tan

BR (SM) = (3.70 0.30) x 10 –4

Good agreement with CLEO & Belle :

BR (exp) = (3.34 0.68) x 10-4

New Physics Searches in rare decays (examples)

SM (3.4 0.5) x 10 -9

SUSY : (tan )6 could reach 10-6 !

Tevatron : (bb) 100 b sensitivity !

• b s

New CDF upper bounds on BR( Bs,d ) :

Br(Bd ) < 1.5 x 10-7

Br(Bs ) < 5.8 x 10-7

For Bd0 :

Slightly better than

Belle 2003 !

hep-ex/0403032 Submitted to PRL

stops + charginos

Note: SUSY constraints are model-dependent

• Bd,s +-

M (GeV)

J/

’ (1S,2S,3S)

SM signal

X 106

Similar sensitivity from D0

i.e. not much room for SUSY here …

_

(mixing in the down squark sector)


• underestimation of isospin breaking corrections to the data due to -0 mass splitting? … controversial …

The muon anomalous magnetic moment

• reevaluation of part of aLBL

would shift the expected value by ~ + 50 10-11

(g-2) sensitive probe to New Physics …But uncertainties on the SM prediction :

Winter 04

Recent developments :

from had

from e+e- had

aHAD ?

aexp = 11 659 208 (6) x 10-10

• Summer 03: revised analysis of CMD-2 data better agree with , but still… • exp. measurement of E821 using - : average value goes up a bit

(+ & - combined) 0.5 ppm !

• e+e- 4 at BaBar using ISR photons : somehow in-between e+e- & , closer to data …

• (e+e- ) by KLOE at DANE (s 1 GeV) :

confirms the other e+e- measurements …Still puzzling… but new data from BaBar and KLOE might help understand…

Disagree…

(Davier, hep-ex/0312065; Ghozzi & Jegerlehner, DESY 03-155)

(Melnikov & Vainshtein, hep-ph/0312226)

2.7

1.4

hep-ex/0407048


- upper bounds on M(chargino) & M(sleptons) encouraging for collider searches although ’s and l might be too heavy for Tevatron… - encouraging for direct 0 CDM searches

SUSY Searches and a

| aSUSY | tan / m2

SUSY

At large tan :difficult to have chargino & sleptons both light

e.g. aSUSY < 80 x 10-10

(

p)

(pb)

M ( LSP )

CDMS II, Edelweiss II

In any case, aSUSY cannot be too large !

> 0aSUSY

> 0

M (

sm

uon )

500

M ( chargino ) 100000

tan = 50

tan = 20

(very conservative)

Baltz & Gondolo, PRD67, 06503 (2003)

Martin & Wells,PRD67, 015002 (2003)

1000

10-6

Encroaches on the “trileptons” domain of the Tevatron

~

e.g. if aSUSY > 11 x 10-10

100

10-10

If aSUSY “signal” is confirmed :

(squarks & Higgs not too heavy i.e. (p) not too small) NB : however can have large (p) while a

SUSY 0 …

15

Constraints & Sensitivities on mSUGRA

tan = 55tan = 10

100 1000m1/2 (GeV)

m0 (

Gev)

10

100

1000

“focus point”, WW

- co-annihilationRequires m O(10 GeV)

sfermion exchange

- l coannihil.

LSP

too large

Plots from L. Roszkowski hep-ph/0404052; bounds from V. Bertin et al. hep-ph/0204135, Run II Workshop hep-ph/0003154

If DM = 01 : 2 bounds from WMAP 0.095 < LSP < 0.13 Very precise !!

White domains allowed if 01 is only a part of the CDM

aSUSY not too large

TrileptonsRun II

CDMS II,Edelweiss II

fr

om S

un (Antares, Icecube)

LHC

10 fb

-1

100 fb

-1

m1/2 (GeV)1000100

100

1000

m0 (

Gev)

Run II3-leptons CDMS II,

Edelweiss II

from SunLH

C 1

0 fb

-1

100

Bs < 2 x 10-8

1 x 10-8

“funnel”, A

~&

~


Beyond Minimal SUGRA…mSUGRA is becoming very tightly constrained… But (examples of way-outs) :

• SO(10) SUSY Grand Unified Theories

• Relaxing universality : constraints on LSP much more easily fulfillede.g. increase M1 or decrease M3 m( ) decreases co-annihilation Lower M3 q & g searches at the Tevatron not so severely constrained by LEP…

Large interest, e.g. in view of neutrino masses !

Minimal models not so severely constrained by LSP (lighter A)1st & 2nd gene. sfermions are heavy ! i.e. no effect on (g-2)Large tan sensitivity of Bs at the Tevatron !Direct DM searches : 10-9 – 10-7 pb, i.e. encouraging May see e in the difficult “funnel” region !

• DM mainly consists of something else …

0 DM if Rparity = (-1)3B+L+2S is not conserved …Might affect rare decays e.g. K For neutrinos : mechanism to generate (Majorana) mass terms

At colliders : single production of SUSY particles, less Emiss

(axions, gravitinos, axinos, Kaluza-Klein states,…)

In some cases, might expect stable or t~ ~

Search for charged slowly moving particles (TOF)

Stable stopabove 100 GeV

Belanger et al., hep-ph/0407218

m2atm m2

t / MGUT

Yt = Yb = Y = Y

~ ~

e.g. Masiero & Vempati, hep-ph/0407325

17 E. Perez

’131 = 0.3H1 Collab., hep-ex/0405070

M(s

bott

om

) (G

eV

)

M(stop) (GeV)

H1 Collab.,PLB 561,241 (2003)

Rp and the HERA events with lepton +

PT,miss

HERA-I, 105 pb-1 :

Assume heavy gauginos & light sbottom.

PTX

(W prod) 1 pb

H1 e+ p dataCombined e &

PTX > 25 GeV 10 / 2.92

0.49

PTX > 40 GeV 6 / 1.08 0.22

Example : resonant stop production at HERA via ’131

e

_

Dominant decay : t b W jet + P T,miss + W Main bckd when W l :

• Data not consistent with t production (3 chan)• Other interpretations considered e.g. FCNC top

~

~ ~

(HERA-I) No such excess in ZEUS (but candidates in channel)HERA I & II, e & HERA I & II, e &

H1 Prelim.,

163 pb-1

H1 in HERA-II data

(45 pb-1) :8 new events,

3 at PTX > 25 GeV

At PTX > 25 GeV :

Nobs = 14

Nexp = 5.1 1.0 Stay tuned !!!

Rp

(includes e-p HERA-I data)

18 E. Perez

Apparent symmetry between the lepton & quark sectors ?Exact cancellation of QED triangular anomaly ?

e e

Lepton + Quark Resonances : Leptoquarks

(unknown) Yukawa coupling lepton-quark-LQ

• LQs appear in many extensions of SM (enlarged gauge structure, compositeness, technicolor…)

• Connect lepton & quark sectors • Scalar or Vector color triplet bosons• Carry both L and B, frac. em. charge

ZEUS e+p94-00

ZEUS, PRD68 052004 (2003)ej channel at HERA

Look for a resonant peak in M spectra reduced background

cf Rp squark

s

CDF Run II Prelim.,191 pb-1

jj channel at Tevatron

Large bckgd, but well controled

Not an easy channel !

Rencontres du VietNam, 08/0419

2nd (and 3rd ) generation LQs also looked for at the Tevatron.For LQ j, similar sensitivity asfor LQ ej.

Constraints on 1st & 2nd generation Leptoquarks

e Run II bounds

1 238 D0

1 232 CDF (LP’03)

0.5 145 D0 (eejj)0.5 197 D0 (ejj)0 117 CDF

D0 Run II + Run I : M > 253 GeV for =1

• Tevatron probes large masses for large

e independently of

• HERA better probes LQs with small provided that not too small

Complementarity of both facilities

e = BR( LQ eq )

=

BR

(LQ

e

q)

MLQ (GeV)NB : at HERA, e+ / e- + polarisation could help in disentangling the LQ quantum nbs

(LP’03)

CDF II Prelim,198 pb-1

M(LQ2) > 241 GeV

2nd gene, = 1

E. Perez

20 E. Perez

Searches for new resonances : dilepton

• New heavy gauge boson Z ’, e.g. L-R models, or E6 GUT inspired, Little Higgs Z’…• Kaluza-Klein gravitons in some extra-dim. models • (Color-singlet) technirho in Technicolor models …

ee DY,QCD “fake”

DY

D0 & CDF searched for ee & resonances :

Z’ Run II direct bounds between 570 & 780 GeV

Z’ Run II direct bounds between 570 & 780 GeV

Main bckgds @ high M :

For E6 inspired models,already competitive with indirect LEPbounds (430-670 GeV)

200 pb-1

First constraints (direct) on “Little Higgs” models !

CDF II Prelim, 200 pb-1

Z’H ee

200 pb-1

Z’ Bounds D0 Run II Prelim.

95% CL

SM couplingsE6, E6, E6,

780 GeV(although “minimal”models predictheavier ZH, 2-6 TeV)

ZH

q

q_

cotan

• “LittleHiggs”

eeee

E. Perez

21 E. Perez

Kaluza-Klein Gravitons

Why is the gravity so weak, i.e. MPl >>> MEW ?

All attempts higher dim. space, with n compactified extra dimensions

• “Strong gravity” ; fundamental scale ~ TeV; gravity appears weaker in 4d because flux lines are “diluted” in large extra dim. Large Rc 0.1 mm. Not excluded by gravity measurements Arkani-Hamed, Dimopoulos, Dvali, PLB 429 (1998) 263 revived ideas from Antoniadis, PLB 246 (1990) 377.

Randall & Sundrum models; “usual” version : n=1, Rc Planck length

• “Localized gravity” on a “brane” at d 0 from our brane; propagation of gravity in the extra dim is exponentially damped due to the (tuned) space-time metric

In localized gravity :

G(k) heavy, G(1) TeVCoupling of G(k) to SM fields TeV

(determined by some model param, k/MPl 0.1)

PRL 83 (1999) 3370; PRL 83 (1999) 4690

Spin 2resonanc

e

Couplin

g k

/MPl

G(1) mass (GeV)

Graviton propagate in extradim Kaluza-Klein modes

For k / MPl = 0.1 : masses below

690 GeV ruled out at 95% C.L.

For k / MPl = 0.1 : masses below

690 GeV ruled out at 95% C.L. Most stringent collider bounds

so far.

345 pb-1

(also D0 Prelim, ee final states)

ee


Kaluza-Klein Gravitons in Large Extra Dim

Very different phenomenology if “large” extra dimensions.G(k) with quantized momentum qT = k/R in extra dim :

m2 = 0 = ( E2-p4d2 )-qT

2 m4d2 = qT

24+n dim 4 dim

Massless graviton G(k) Massive graviton G(k)

with momentum qT = k/R

with m2 = k2/R2

R 0.1 mm i.e. 1/R 1 meV Mass “continuum”, “first” states very light !!

n=2 : MD > 1.6 TeV

n=4 : MD > 0.9 TeV

n=2 : MD > 1.6 TeV

n=4 : MD > 0.9 TeVcompensated by huge multiplicity of states

1 / MPl

Coupling of G(k) to SM fields 1 / MPl G(k) stable ! • Direct production at colliders

e+e- G (k)

• Indirect effect on SM aplitudes due to virtual exchange :

Effective coupling : A / MS4

Tevatron 2 fb-1 MS up to 2 TeV

D0 Run II Prelim.

200 pb-1ee & ee &

D0 Run II + Run I, ee & : MS > 1.43 TeV

SM + MS = 1.1 TeV

QCD“fake” Most stringent collider bound

ADL Prelim., Summer 04

E. Perez


Conclusions

The search for new physics is a very active field.

Tevatron & HERA are working very well, the experiments might “see” something in the near future !Constraints set on many models, often the most stringent up to date.

The example of SUSY searches shows the nice complementarity betweendifferent experimental approaches :direct searches, rare decays, precision measurements, Dark Matter searches …

“Searches” is a very rich field of physics.

It is likely to remain the case – even more ? – after direct evidence forNew Physics at (e.g.) the LHC( if SUSY : consistent value for LSP, additional CP phases, mixing in the

squark sector, possible relations with the mixing etc …)

No doubt that using most of the experimental data to reach the understanding we aim at will be fun !


Backup & Divers…


“Signature Based” Searches for NP(Quasi) “model-independent” search for new physics :• definition of objects (e, , , , jet, W, Z, …)• look at data vs SM in all “channels” with > 1 object• in each channel, find the part of space with largest deviation (e.g. in M, pT )• quantify the agreement using “Gedanken” (Mock, MC) expts

Pionnered by DZero with the full Run I sampleD0, PRD64, 012004 (2001)

Applied recently to the full sample of H1 data

# Events

2B

3B

4B

-j-

Requires a very good understanding ofdetector & backgrounds !

• overall very good agreement H1 data / SM• retrieves the “lepton-jet-ET,miss” and

“multi-electron” anomalies (dedicated analyses might be more sensitive)

H1, contrib paper #195

H1 Prelim

HERA-II

45 pb-1


CDF Run II, 75 pb-1, Prelim.

Resonance mass (GeV)

X

BR

(p

b)

Excited quarks & other j-j resonances

• Dijet resonances predicted in various modelsq q

g g

q*

fs /

- New fermions, e.g. excited quarks expect signal in q /Z, q W depending on fs vs f & f’

- new gauge bosons, Z’, W’ (but signal mainly in the dilepton channels)

- new massive colored bosons, e.g. SU(3)1 x SU(3)2 SU(3)QCD

( chiral color, colorons, topgluons…)

• Look for a narrow resonance in the di-jet spectrum : use a simple background parametrization for d/dM and search for bumps resolution

Narrow resonances

compared to(Mjj) 10% Mjj

200 1100

1

10

• Axigluon & (flavor univ.) colorons :

assuming (qqg) = (qqG)

M > 1130 GeV

First direct bound > 1 TeV !!First direct bound > 1 TeV !!

• Excited quarks :

M > 760 GeV

(f=f’=fs=1, = M)


HERA events with isolated lepton + PT,miss

HERA I data

HERA I

Documents

Emmanuelle PEREZ CEA-Saclay, DSM / DAPNIA / Spp