Higgs Bosons through Experiments

Zeinab Shafiee

25.10.2011IMPRS Retreat - Hamburg

Why looking for Higss Boson?

• Answering the question of Mass

• The single missing piece of the Standard Model yet to be spotted

• The Higgs boson might not only interact with the particles of the Standard model , but also with WIMPS that may form dark matter (2009)

• Universe at the very first moments

Having available four production mechanisms is a key for measurements of Higgs parameters

http://dorigo.wordpress.com/2007/09/17/update-on-higgs-searches-cdf-wh-lv-bb/

• 1989-2000LEP collider at CERN(lower bound for the mass of the Standard Model Higgs boson of 114.4 GeV/c2 at the 95% confidence level)

• The LEP was shut down in 2000 due to construction of LHC (which its full operational mode was delayed until mid-November 2009 because of technical problems)

• The search was continuing at Fermilab’s Tevatron (6.3 km) in Illinois (until Sep 2011)

LHC the Big Bang Machine

• 27km circular tunnel under the French-Swiss border• The tunnel is buried around 50 to 175 m. underground• 16 years• 10 billion $

How does it work?

http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm

• Two beams of proton smashed together at crossing points ATLAS detector• Trillions of protons will race around the LHC ring 11 245 time/second• Speed : 99.9999991% the speed of light • Maximum energy of 7 TeV (tera-electronvolt) each and in a head-to-head collisions of 14 TeV• 600 million collisions will take place every second.

http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/

• Ultrahigh beam vacuum 10-10 Torr (~3 million molecules/cm3) , avoiding collisions with gas molecules

• Squeezing the beam size down at the collision point to increase the chances of a collision

Proton Proton Collision

http://hands-on-cern.physto.se/ani/acc_lhc_atlas/lhc_atlas.swf

Detectors

http://hands-on-cern.physto.se/ani/acc_lhc_atlas/endview.swf

What is the result?

Status as of March 2011, to the indicated confidence intervals(Fermi Lab http://www.fnal.gov/pub/presspass/press_releases/Higgs-mass-constraints-20100726-images.html)

What’s going on?

• Lepton Photon Conference (Mumbai India, from 22 to 27 August 2011)

New results were presented but all eliminate the mid-range where the Higgs - if it exists - might be found

• Cern research director Sergio Bertolucci (in August 2011):

"Discoveries are almost assured within the next 12 months. If the Higgs exists, the LHC experiments will soon find it. If it does not, its absence will point the way to new physics."

And if it does NOT exist???Higgsless Models

See Zahra’s talk

And Thank you!

References• http

://www.digitaltrends.com/cool-tech/cern-higgs-boson-god-particle-likely-does-not-exist/

• http://www.bbc.co.uk/news/science-environment-14596367• http://www.exploratorium.edu/origins/cern/ideas/higgs.html• http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/• http://

atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/Conferences/2003/aspen-03_dam.ppt• http://en.wikipedia.org/wiki/Higgs_boson• http://press.web.cern.ch/public/en/LHC/Facts-en.html