Search for New Phenomena at Colliders

Search for New Phenomena at Colliders

Pedro Mercadante LISHEP2006

LISHEP 2006 Pedro Mercadante 2

Outline New physics at TeV scale ? Supercolliders Tevatron LHC ILC Conclusions


Beyond the Standard Model

We don’t know the EW breaking sector Neutrinos have masses Dark matter Why three generations ? Does not include gravity!

Should be viewed as an effective Should be viewed as an effective theory valid theory valid

up to a mass scale up to a mass scale


SM Higgs mass Upper and lower

Higgs mass bound as a function of Λ, the scale where SM breaks down


Why is TeV scale special? It is the scale of EW symmetry breaking We don´t know how masses are

generated In the Standard Model the Higgs

mechanism is evoked

“ this theory is sometimes dignified with the title `the minimal standard model´, but its is not really a model at

all ” Murayama and Peskin (hep-ex/9606003)


Hierarchy Problem Quadratic divergencies for Higgs

Mass Huge cancellations to keep its

mass at EW scale Scale for new physics near TeV or ... New Symmetry that protects the

scalar sector Supersymmetry


Supercolliders


Minimal extension of SM Pair production of heavy quarks Pair production of heavy leptons New electroweak Gauge Bosons

Technicolor The minimal technicolor model The Farhi-Susskind model Single production of Technipions Pair production of Technipions

Supersymmetry Superpartner spectrum and elementary cross sections Production and detection of strong interacting

superpartnes Production and detection of color singlet superpartnes

Composite quarks and Leptons Manifestation of Compositness Signals for compositeness in High pt Jet Production Signals for composite Quarks and Leptons in Lepton

pair production


Recomendations Detectors

Detection and measurement of W and Z in their non leptonic decay modes

Missing transverse energy is an important signal. Detectors should be hermetic covering the |η| < 3 region

Ability to tag and measure heavy quarks and tau leptons Accelerator

40 TeV collider with L= 1039 cm-2 (1 fb-1) will make possible to explore the TeV scale

For a 10 TeV device the same guarantee cannot so comfortably be made even at a L=1040 cm-2


Past and Future Accelerators


Where we stand Tevatron Run I and LEP

Eletroweak theory tested as quantum field theory at the level of one per mille

Signal for Higgs in global fits? Top quark discovered with mass of 175 GeV Quarks and leptons are structureless on the TeV

scale Others (colliders and non colliders)

Neutrino oscilation (and mass?) BB factors shows CP violation in B0 decays Flat Universe dominated by dark matter and energy Tau neutrinos


Standard Model Measurements Several parameters

measurements and its SM pull

Higgs Mass from radiative corrections


Hierarchy Problem New Symmetry that protects the

scalar sector Supersymmetry Extra Dimensions

Is gravity at TeV scale? (LED) Are there new mechanism to protect

the weak scale ? (Randal-Sundrum) Some kind of new physics at TeV?

(UED)


Tevatron Run II Accelerator

pp 2 TeV L = 1 fb-1

Detectors Hermetical b id

InjetorRecycle

r

Tevatron

Chicago

Antiproton

p

p CDF

DØ


Integrated Luminosity


New Physics Program Recent DZero

papers topics: Excited states Leptoquark Technicolor Supersymmetry Extra Dimensions

Similar for CDF

Analysis subgroups: Jets and Missing ET

Leptons and Jets Multileptons High pT Leptons Taus


LHC (first Supercollider)

Acelerator pp 14 TeV L = 100 fb-1/year

Detectors |η| < 5 Jet id


Physics Program Atlas Physics

Group B physics Top Standard Model Higgs SUSY Exotics Heavy Ions Monte Carlo

Generator

Performance Groups e/gamma Jets/ETmiss b-tagging muon


ILC (Linear collider)

Acelerator e+ e- Polarized beams Tunable Energy Energy = 0.5, 1, 1.5

TeV? L = 100 fb-1/year

Detectors |η| < 5 Jet id

Cleaner environment

Can we have different (complementary) information ?

What can we gain running the two at the same time?


Case Study: Supersymmetry Symmetry that relates bosons and

fermions Is it related with the EW scale?

SUSY must be broken!SUSY must be broken!

How to break it ?How to break it ?


The MSSM Two Higgs doublet

SM + Superpartners

µ parameter Tan Superpotential

Soft Terms Scalar Masses Gauginos Masses Trilinear (A)

Parameter Bilinear (B)

Parameter

More then 100 new parameters

u

uudddlud

HLLQDLQDLLE

UHQfDHQfEHLfHH

'''

W


Gauge Unification

SM

1 TeV

10 TeV


Problems! How to make predictions? If we allow general terms for SUSY

breaking there are new contributions to FCNC and CP violation process.

Fine tunning again ?Fine tunning again ?

How SUSY is Broken ?How SUSY is Broken ?


Typical event at LHC


Pictorial View

Hiddensector

MSSMsector

MessengerSector

gravity

gaugenew gauge


ConsequencesmSUGRA Soft parameters

at Planck scale. Unification ? Small number of

parameters. FCNC supressed.

GMSSB: Small Gravitino

mass. Soft parameters at

Messenger scale. Masses

proportional to gauge couplings.

FCNC supressed.RGE equations to evolve soft

parameters to EW scale


Radiative EWSB

2 2 2H H2 2

z 2

m m tan1m

2 tan 1d u b

bm

-= -

-


R parity conservation ?

u

uudddlud

HLLQDLQDLLE

UHQfDHQfEHLfHH

'''

W

Lepton and barion number violation

The LSP is Stable (DM ?)


Signals for SUSY The LSP is stable and neutral

Missing Energy! At Tevatron energies chargino

productions dominates for gluinos heavier then 300 GeV

At LHC gluinos and squarks cross sections dominates up to 1 TeV


Tri-lepton signal (Tevatron) Signal depends on σ X BR


Sbotton Searchs (Tevatron)

Model independent if sbotton is light and few particles are available

Need good b-tag


The Higgs Sector in the MSSM Constrained two Higgs doublet

model. 5 physical Higss: h, H, A and H. The lightest Higgs is necessary

light. mh < 140 GeVmh < 140 GeV


mSUGRA Phenomenology

Common scalar masses (m0) Common gauginos masses (m1/2) Tanβ Common A-term Sign of μ

Parameters:


Baer et al JHEP 06 054


LSP as a candidate for DM? Neutralino: neutral

heavy stable particle.

Good candidate for CDM.

In a given framework it is possible to calculate neutralino contribution to CDM.

Recent data from WMAP gives:

ΩCDM h2 =0.1260.008

We can see what are mSUGRA prediction



FP


Focus Point Region Squarks masses > 2 TeV Gluino mass > 1.5 TeV Is this Natural?

2 2 2H H2 2

z 2

m m tan1m

2 tan 1d u b

bm

-= -

-


Small µ region Gluino decays

mainly in b´s and t´s

Does b tag helps?


Mg=1650 GeV Mg=3.5 TeV

ILC Reach

Baer et al JHEP 0510:020


LHC Measurements L=300 fb-1

End point mass distribution

Mass differences measurements

Hint for LSP


ILC Measurements K. Desch et al studied the

chargino pair production at ILC

Chargino masse can be measured to be 117.1 (0.1) GeV (scan)

Neutralino mass can be measured as 59.2 (0.2) using the decays

B.C. Allanach et al hep-ph/0602198

Bean polarization CM energy scan Will narrow the

parameter space


Conclusions: TeV scale will tell us the mechanism of

EW symmetry breaking The LHC will be able to explore this scale An ILC would be very important to fully

explore this scale. It will be important to determine the parameters of several scenarios

From a look at history, LC and Hadron colider synergy are important: top quark, J/Ψ, Z …


Monte Carlo Tools Workshop Scheduled for March 20-21 Theoretical physicist Peter Skands uses Monte Carlo methods to decide between the many possible outcomes of quantum interactions.What do roulette and particle collisions have in common? The laws of chance decide--the same input can result in many different possible outcomes. In the former example, the ball can land on one of 38 possible slots; in the latter, the same kind of matter and antimatter can produce collisions that create hundreds of different possible high-energy events. Until each outcome actually occurs, it exists only as a probability. "Monte Carlo tools are a way of simulating particle collisions in full glorious, gory detail," says Peter Skands, a theoretical physicist on the workshop organizing committee. "They take the elementary scattering process and dress it up with all the radiation, resonance decays, hadronization, and leftover beam remnants that are part of a real particle interaction." Such simulations allow scientists to make detailed comparisons between the thing they want to find (such as the signature of a Higgs boson) and the background events that may confuse such signatures.

The Monte Carlo Tools for Beyond the Standard Model Physics workshop on March 20-21 will focus on some of the most exotic possibilities for new physics that theorists consider today. The agenda spans over extra dimensions (your choice of warped, straight, or universal), top partners, and Higgsless models, among others. "I think at the moment we are well prepared to deal with supersymmetry (SUSY); however, that's just one idea among many for what might be lurking there at the Terascale. If it's not SUSY but something else, you want to know you're prepared for it," says Skands. "As the Tevatron collects more luminosity and the LHC approaches, it's important to ask: Are our theoretical descriptions sufficiently accurate? How precisely can the parameters of the new physics be measured? To do this reliably, you need Monte Carlo simulations." Web registration is now closed but people can register onsite the day of the workshop. The program is available on the workshop Web page. — Dawn Stanton

Search for New Phenomena at Colliders

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