Electro-Weak and Beyond Standard Model working group report

1. 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

2. Status of the main accelerators HERA (H1, ZEUS) TEVATRON (CDF, D0) All major accelerators are at their peak! Results are continuously updated, a lot of fresh results presented PEP-II (BaBar) KEKB (BELLE) 2

3. Summary of the Electro-Weak results Top quark mass A precise measurement is the main goal of the experiments at the Tevatron • 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 scaleuncertainties which is the main systematics. • Matrix Element: defines a likelihood for each event based on the differential • cross 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. • …and channels: • Lepton + jetsat the moment the best compromise between background and statistics • dileptonvery clean, low statistics yet but starts to become important • all hadroniclarge statistics buthigh background, not competitive at the moment will contribute in the future 3

4. Top-mass – combination of Tevatron results Top mass [GeV] 4

5. Other Top properties just about to become accessible, sensitivity to possible BSM physics W helicity:SM right-handed W from top decay suppressed by V-A coupling Experimentally accessible via lepton pt, cosq* (angle between charged lepton and top in W rest frame) Top charge: SM Q= +2/3e -4/3e possible for BSM models CDF D0 A first D0 analysis excludes Q= -4/3e @ 94%CL 5

6. Top cross section WEIGHT 11% 32% 50% 2% 6% -2% BEST SINGLE σMEASURED CDF COMBINED σtt=7.3±0.9 pb 15% improvement w.r.t best single σmeasured 6 Susana Cabrera, IFIC(CSIC-UV)

7. Susana Cabrera, IFIC(CSIC-UV) Top cross section Good agreement with SM prediction 7

8. W/Z cross section 8

9. Di-boson production q q 9

10. Ask the speaker for LEP comparison 10

11. Top @ LHC 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 reconstruction Many detector properties involved Crucial role in detector commissioning Interesting results already with 1-10 fb-1 Goal for LHC:dm ~ 1 GeV/c, other properties with unprecedented precisions Signal at the beginning, bg in the second LHC phase (main bg for most exotic processes) 11 Mario Paolo Giordani, Udine University and INFN Trieste

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14. Riccardo Ranieri, University and INFN Firenze CERN/LHCC 99-15 ATLAS TDR 15 CMS NOTE 2003/033 Higgs @ LHC • After detector calibration and LHC pilot run… • …almost all the “allowed” mass range can be explored during the first year (10 fb-1) • ...after 2 years (≈30 fb-1) 7σ significance over the whole mass spectrum, covered by more than one channel Strong competition in ~ 2009 between LHC and Tevatron for a possible Higgs discovery 14

15. LHC as a High Energy gg Collider p p RP p p Phys. Rev. D63 (2001) 071502(R) hep-ex/0201027 • Highlights: • gg CM energy W up to/beyond 1 TeV (and under control) • Large photon flux F therefore significant gg luminosity • Complementary (and clean) physics to ppinteractions, eg studies of exclusive production of heavy particles might be possible opens new field of studying very high energy gg (and gp) physics Measure (gg) X in the CMS or ATLAS detector and the scattered protons using very forward detectors.. ..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 (talk by J. Whitmore) …or, Proton Detectors at 420m from IP1/5: FP420 (talk by B. Cox) K. Piotrzkowski UCLouvain 15

16. 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 16 K. Piotrzkowski UCLouvain

17. Shima Shimizu 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 17

18. Wolfgang Menges Queen Mary, University of London Measurement of CKM sides @ the B-factories From semileptonic B decays -> |Vcb| and |Vub| Sides complementary to angles|Vub|/|Vcb| complementary to sin2b • Recent measurements -> |Vcb| determined with high precision (2%)Now |Vub| is important! uncertainties dominated byform factor calculation, work ongoing in close contact between theoreticians and experimentalists to improve the precision 18

19. Tau-physics @ the B-factories g-2 predictions Also performed an estensive study for lepton-flavor violation and tau rare decays Competitve results in the realm of high precision measurement No departure from SM expectations observed up to now 19 Eugenio Paoloni, INFN and University of Pisa

20. Youngjoon Kwon, Yonsei Univ. Radiative and leptonic B-decays @ the B-factories • - Impressive number of channel studied, no deviation from SM observed • B+->t+ n: first evidence by BELLE • ->constrained of CKM parameters 20

21. Y. Iwasaki, KEK Measurement of angles of the unitarity triangle @ the B-factories Summary of the angles measurements Belle and BaBar combined -f1very precise : ~5% - f2andf3constrain 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

22. 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