Electro-Weak and Beyond Standard Model working group report

L. Bellagamba, E. Sauvan, H. Spiesberger

• 23 talks + 5 talks in a joint session with the Structure Functions and low-x WG

• Huge amount of results from HERA, Tevatron, B-factories plus perspectives for the LHC start-up and some theoretical contributions.

It is obviously not possible to cover all the presented results in this summary, interested people can find the details of each talk in the web page of the conference.

1

All major accelerators are at their peak!Results are continuously updated, a lot of fresh results presented

HERA (H1, ZEUS)

TEVATRON (CDF, D0)

PEP-II (BaBar)

KEKB (BELLE)

Status of the main accelerators

2

Top quark mass

Several different method:- Template method: reconstructs a top quark mass in each event and compares the distribution of Mtop_reco with template distributions derived from model calculation to estimate Mtop. The jet energy scale is constrained requiring that the hadronically decaying W from a final state consistent with the known W mass and width -> improvement in the energy scale uncertainties which is the main systematics.

A precise measurement is the main goal of the experiments at the Tevatron

…and channels:- Lepton + jets at the moment the best compromise between background and statistics- dilepton very clean, low statistics yet but starts to become important- all hadronic large statistics but high background, not competitive at the moment will contribute in the future

Summary of the Electro-Weak results

-Matrix Element: defines a likelihood for each event based on the differentialcross section (function of Mtop) multiplied by the transfer function from jet to parton energies -> the jet energy scale parameter is included in the likelihood via the transfer function and takes part in the maximum likelihood fit.-Decay length technique: top mass correlated to the boost of the b-quark larger mass ->larger decay length. Still not competitive due to the current statistics, but very interesting since relies purely on tracking -> no jet energy scale uncertainty.

3

Top-mass – combination of Tevatron results

Top mass [GeV]

4

Other Top properties

W helicity: SM right-handed W from top decay suppressed by V-A couplingExperimentally accessible via lepton pt, cos* (angle between charged lepton and top in W rest frame)

Top charge: SM Q= +2/3e -4/3e possible for BSM models

just about to become accessible, sensitivity to possible BSM physics

CDF

D0

A first D0 analysis excludes Q= -4/3e @ 94%CL

5

CDF COMBINEDσtt=7.3±0.9 pb 15% improvement w.r.t best single σmeasured

WEIGHT

11%

32%

50%

2%

6%

-2%

CDF

BEST SINGLE σMEASURED

Top cross section

Susana Cabrera, IFIC(CSIC-UV)6

Top cross section

Good agreement with SM prediction

Susana Cabrera, IFIC(CSIC-UV)

7

W/Z cross section

8

Di-boson productionq

q

9

Ask the speaker for LEP comparison

10

Top @ LHC

Mario Paolo Giordani, Udine University and INFN Trieste

At the very beginning ideal channel for initial studies

Exploit tt lepton+jets• 2 b-jets• 2 light jets• 1 high-pT lepton+missing ET

easy to trigger (high high-pT lepton) W and top mass reconstructionMany detector properties involvedCrucial role in detector commissioning

Interesting results already with 1-10 fb-1

Goal for LHC: m ~ 1 GeV/c, other properties with unprecedented precisionsSignal at the beginning, bg in the second LHC phase (main bg for most exotic processes)

11

12

13

After detector calibration and LHC pilot run…

– …almost all the “allowed” mass range can be explored during the first year first year (10 fb-1)

– ...after 2 years 2 years (≈30 fb-1) 77σσ significance over the whole mass spectrum, covered by more than more than oneone channel

CMS NOTE 2003/033CERN/LHCC 99-15 ATLAS TDR 15

Higgs @ LHCHiggs @ LHCRiccardo Ranieri, University and INFN Firenze

Strong competition in ~ 2009 between LHC and Tevatron for a possible Higgs discovery 14

Highlights:• CM energy W up to/beyond 1 TeV (and under control) • Large photon flux F therefore significant luminosity• Complementary (and clean) physics to pp interactions, eg studies of exclusive production of heavy particles might be possible opens new field of studying very high energy (and p) physics

LHC as a High Energy Collider

pp

Phys. Rev. D63 (2001) 071502(R)hep-ex/0201027

Measure ( ) X in the CMS or ATLAS detector and the scattered protons using very forward detectors.. p

p

RP

..i.e. ‘Roman pot’ detectors put as far (> 100 m) from the IP and as close to the beam (2 mm) as possible

Proton Detectors at 220m from IP5: Totem Proton Detectors at 220m from IP5: Totem (talk by J. Whitmore)……or, Proton Detectors at 420m from IP1/5: FP420 or, Proton Detectors at 420m from IP1/5: FP420 (talk by B. Cox)

K. Piotrzkowski UCLouvain15

• High-energy (at electroweak scale and beyond) photon interactions have significant cross-sections at the LHC!

• This offers new, exciting and complementary physics studies in parallel to ‘nominal’ ones

K. Piotrzkowski UCLouvain16

Combined EW-QCD fit @ HERA

HERA II data:In addition to much statistics, polarization gives direct sensitivity to EW.ZEUS: combined fit to extract quark couplings to Z in NC polarised data

Axial/vector couplings of u/d-type quark: 4 couplings

2 of them are free and fitted together with PDFs

Shima Shimizu

17

Measurement of CKM sides @ the B-factoriesWolfgang Menges Queen Mary, University of London

From semileptonic B decays -> |Vcb| and |Vub|

Sides complementary to angles|Vub|/|Vcb| complementary to sin2

•Recent measurements -> |Vcb| determined with high precision (2%) Now |Vub| is

important! uncertainties dominated by form factor calculation, work ongoing in close contact between theoreticians and experimentalists to improve the precision

18

Tau-physics @ the B-factories

g-2 predictions

Also performed an estensive study for lepton-flavor violation and tau rare decaysCompetitve results in the realm of high precision measurementNo departure from SM expectations observed up to now

Eugenio Paoloni, INFN and University of Pisa19

Radiative and leptonic B-decays @ the B-factories

Youngjoon Kwon, Yonsei Univ.

- Impressive number of channel studied, no deviation from SM observed- B+ -> : first evidence by BELLE ->constrained of CKM parameters

20

Measurement of angles of the unitarity triangle @ the B-factories

Y. Iwasaki, KEK

Belle and BaBar combined Summary of the anglesmeasurements

1 very precise : ~5%2 and 3 constrain the unitarity triangle but the precision is statistically limited . More data will improve precision in the near future

Very good agreement between measurements and SM

However much more data are expected from B-factories in the next few years, surprises cannot be excluded.

21

Conclusions

The message from the EW results presented is:

the Standard Model is still in perfect shape

No convincing sign of any deviations seen both in high energy and high precision studies.

Nevertheless the next few years will be really exciting for high energy physics.The SM Higgs, thanks to the increasing precision in the EW measurement, is framed. In three years from now all the possible mass range will be scanned both by the Tevatron and the LHC experiments.

Moreover possible surprises could also arise from high-precision measurements at the B-factories which should double their statistics in a couple of years or from searches at the high energies colliders

but this is the topic of the next talk........

22