Transcript What is new at CERN? - Vanderbilt HEP

Compact Muon Solenoid (CMS) Physics,
Status, and Plans
Bill Gabella and Med Webster
QuarkNet 2013
Vanderbilt University
Outline
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The Standard Model of Particle Physics
The Large Hadron Collider
The Compact Muon Solenoid
Proton on Proton collisions
● Higgs Boson, now your run-of-the-mill Standard Model Higgs
● Supersymmetry, NOT?
● Extra Dimensions
Lead on Lead collisions
● centrality, Jet Quenching
● ridge in two particle correlations
Large Hadron Collider and CMS plans
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Particle Physics,
aka High-Energy Physics,
aka Theory of Fundamental Particles
All stable matter is made
of protons, neutrons, and
electrons.
Yes, but protons and
neutrons are also made
up of Quarks!
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The Standard Model
A good description of fundamental particle interactions, relevant inside the
nucleus, at early times in the evolution of the universe, and in man-made
and natural collisions of particles.
Particles that “carry” the force.
Particles that make up Matter.
All of the matter and forces in the Universe are made up of:
6 leptons (and 6 anti-leptons), 6 quarks (and 6 anti-quarks), and 12 force carrying
particles...ur plus the Higgs boson and don't forget Gravity, and...
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Ref: http://www.particleadventure.org
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Cosmic Ray
Showers
Mostly Protons with
high energy hitting
the atmosphere...
make mostly muons
at Earth.
Ref: http://www.particleadventure.org
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Particle Accelerators
Large Hadron Collider, p on p
Geneva, Switzerland
7, 8, and soon 14 TeV
center of mass
Tevatron, was p on p-bar
Batavia, IL (Chicago)
2 TeV center of mass
now lower energy, high intensity p
source, also intense neutrino source
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Ref: www.fnal.gov, www.cern.ch
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The Large Hadron Collider
Proton-on-Proton collider, 2010-11 3.5+3.5 TeV center of mass energy
2012
4+4 TeV
plan 2015
7+7 TeV
also Lead-on-Lead (aka Heavy Ion) collider
and Proton-on-Lead for comparison of the above two
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The Large Hadron Collider
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The Large Hadron Collider
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Large Hadron Collider (LHC)
Energies:
Linac 50 MeV
PSB
1.4 GeV
PS
28 GeV
SPS 450 GeV
LHC 3.5, 4, 7 TeV
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Ref: Introduction to Accelerators,
Wildner, CERN
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CMS Detector
Vanderbilt University (Will Johns)
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http://www.uscms.org/public_2/about/cms_detector/index.shtml
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Particles through a CMS slice
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The Forward and Barrel Pixel Detector
Barrel Pixel
r = 4.4, 7.3, and 10.2 cm
11520 readout chips, 48 Mpixels
Forward Pixel
z = +/-34.5, and +/-46.5 cm
4320 readout chips, 18 Mpixels
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http://www.hep.vanderbilt.edu/
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borrowed from Mauro Dinardo docdb 2404
CMS - Short Timeline
March 2010 --- Started taking data on collisions at 7 TeV. Previous testing
done at 0.45 TeV (injection energy) and 1.26 TeV. Low
luminosity (intensity)
2010 - 2011 --- Taking data with increasing luminosity (intensity) by both
more proton bunches in the rings and more protons in
each bunch
2012
--- Running at 8 TeV, and high luminosity
July 4, 2012 --- Announce discovery of Higgs-like particle, also seen with
the ATLAS detector
March 2013 --- Shutdown LHC and detectors for “Long Shutdown 1,”
aka LS1. LHC back “on” in 2015 with energy 14 TeV.
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CMS Recent Results - Higgs
July 4, 2012 --- CMS and ATLAS report “Higgs-like particle” at 125 GeV.
Too many H->Gamma Gamma events compared to the
Standard Model predictions for the Higgs.
July 4, 2013 --- The Higgs looks a lot like the Standard Model (SM) Higgs.
Right ratio of different events, better statistics.
Mass 125.8 GeV +/- 0.5 GeV
Now measuring the quantum numbers of the Higgs:
consistent with spin 0 (at least not spin 1 nor spin 2);
parity consistent with +1
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Higgs decays into...
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Higgs to two Z's to Four Leptons
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borrowing from Higgs Seminar
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Note the numbers...
Black dots are data.
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CMS (Some) Other Important Results
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Supersymmetry
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Looking for “missing energy,” i.e. invisible particles,
at least to the detector, as are neutrinos.
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Currently appears to have eliminated many popular
SUSY models; we are left with the 105 parameter
full-model (maybe).
Extra-dimensions
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Inspired by Super-strings, Randall and Sundrum
took the idea of extra-dimensions (spatial) seriously
and asked what would accelerators see/measure.
No discovery, putting
limits
on the models.
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CMS Heavy Ion Collisions
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LHC Collides Pb-208 ions, fully-stripped to +82 charge
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in other words, atomic number Z=82, atomic mass
A=208, number of neutrons N=126
For protons we inject at 450 GeV and ramp up to 3.5 TeV
Acceleration is by electric field, so a charged particle with
charge Ze would be injected at 450 Z GeV and ramp to
3.5 Z TeV total energy.
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The bending magnets determine what energy (really
momentum!) that you can have in your ring of radius
rho.
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CMS Heavy Ion Collisions
p on p
3.5 + 3.5 TeV
Pb on Pb
287 + 287 TeV 1.38 + 1.38 TeV
7 TeV c.o.m.
p on p
4 + 4 TeV
2.76 TeV/u
Pb on Pb
328 + 328 TeV 1.577 + 1.577 TeV
8 TeV c.o.m.
p on Pb
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3.15 TeV/u (??)
4 + 328 TeV
4 + 1.577 TeV/u
just nucleons
5.02 TeV c.o.m.
boosted!
not at rest!
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CMS Heavy Ions, some numbers
Pb-208 accounts for 52.4% of all stable lead.
Z=82, N=126, A=208
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CMS Heavy Ions - A tutorial
well centered or glancing
blow = Centrality
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CMS Heavy Ions - Make a lot of Particles!
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CMS Heavy Ions - Jet Quenching
Main Jet - not modified
In a head-on collision, more Jets
(q-qbar hadron shower) near the
edge of the fireball.
Borrowed from Iancu fig 42.
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Away Jet - highly modified
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CMS Heavy Ions - Jet Quenching
Main Jet - not modified
Away Jet - highly modified
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LHC and CMS Plans
Currently the LHC and all the experiments are doing maintenance.
Expect to start turning on the LHC in 2015, with data taking my
mid-year.
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LHC and CMS Plans
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Backup
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Some Links/References
The Standard Model of Particle Physics
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http://www.particleadventure.org
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Vanderbilt HEP Group http://www.hep.vanderbilt.edu/~focuser/index.php
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CMS Public Talks http://cms.web.cern.ch/org/cms-presentations-public
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CMS News http://cms.web.cern.ch
LHC and Heavy Ions
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Ions Page
http://lhc-commissioning.web.cern.ch/lhc-commissioning/commissioning-ions.htm
http://lhc-commissioning.web.cern/lhc-commissioning/commissioning-ions.htm
LHC consolidations
http://home.web.cern.ch/about/accelerators/large-hadron-collider
http://home.web.cern.ch/about/updates/2013/03/lhc-consolidations-step-step-guide
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Backup
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Units? 1 eV...
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LHC Ions, the Numbers 1/4
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LHC Collides Pb-208 ions, fully-stripped to +82 charge
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in other words, atomic number Z=82, atomic mass
A=208
For protons we inject at 450 GeV and ramp up to 3.5 TeV
Acceleration is by electric field, so a charged particle with
charge Ze could be injected at 450 Z GeV and ramp to 3.5
Z TeV.
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The bending magnets determine what energy (really
momentum!) that you can have in your ring.
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LHC Ions, the Numbers 2/4
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A magnetic field B bends a charged particle with
momentum P in an arc of radius
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Magnet folks like the constant "magnetic rigidity"
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For the LHC ring (and the other injector rings), the B is
set by power supplies and magnets and the rho by the
vacuum pipe
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LHC Ions, the Numbers 3/4
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So you will see people post that we are injecting at
450 Z GeV and ramping to 3.5 Z TeV for each Pb
nucleus (which is a lot, 36.9 TeV injection and ramp to
287 TeV)
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Okay for the physics what is more interesting is the
per proton/neutron energy, so per nucleon the
numbers are less
450 Z/A GeV and ramp to 3.5 Z/A TeV
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Z/A is the average charge per nucleon, 0.4 e, and
finally, inject at 177 GeV/u ramp to 1.38 TeV/u, and
collide at 2.76 TeV/u.
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LHC Ions, the Numbers 4/4
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Bunch populations, from recent posting,
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per bunch charge of 1-1.2e10 ... e's
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Count the Pb ions at +82e each, find there are
12-14e7 Pb ions per bunch (below you will see that
7e7 is the design)
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LHC Ions Injection Chain
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Pixel Numerology
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Barrel has 11520 ROCs, 48 MPxl
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Forward has 4320 ROCs, 18 MPxl
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1 ROC has 4160 pixels
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Si Sensor pixel size is 100 microns by 150 microns
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Fpix has 3 plaquette and 4 plaquette config to its panels: 3
plaquette: 2x5 + 2x4 + 2x3 (ROCs), and the 4 plaquette:
1x5 + 2x4 + 2x3 + 1x2 (ROCs)
Urs shows fpix: (3x24+3x21)/4320 = 2.6% and bpix
(3x16+6x8+3)/1152 = 0.9% not working.
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LHC Ions Physics "Trivia"
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Luminosity is limited by the Electron Capture by Pair
Production (ECPP) at the IPs. That is, the e- from an e+e- pair
produced in the collision is captured by an Pb ion and that ion
is lost on collimators leading to a vacuum problem! Limit is
0.5-1e27 cm^-2 s^-1.
Original choice was Pb+53 after the first foil into LEAR. It was
found that it had an unexpected short lifetime in the electron
cooler, it picked up an e- in a much shorter time than either
Pb+52 or +54. Chose +54 state. Pb+53 ends with a 5p^5
orbital---that looks bad!
While Pb+52 ends with 5p^4 (all paired) and +54 ends with
5p^6.
Beam Loss Induced Vacuum degradation in LEAR, and the
creation of other charge states by Pb+54 interacting with the
beam gas, led to a vacuum spec in LEAR of
1e-12 mbar (LHC can be 1e-9mbar).
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The Standard Model - The Tee Shirt
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The Standard Model - The Details
A pretty equation for the Lagrangian Density of the quantum fields...
Photons, W's, Z's bosons, gluons
Electrons, Quarks, Neutrinos
Higgs “coupled” to leptons
Higgs Particle/Field
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“ In its most explicit form, the Lagranian density of the minimal Standard Model
is given by the somewhat uninspiring expression:” A. Connes & M. Marcolli
gluons
photons
W's and Z's
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Higgs Particle/Field
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The
Standard
Model
The
Details
...there is more...
electrons
up quarks
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CMS Detector
“ In its most explicit form, the Lagranian density of the minimal Standard Model
is given by the somewhat uninspiring expression:” A. Connes & M. Marcolli
Electromagnetic Fields, W's, Z's bosons
Electrons, Quarks, Neutrinos
Higgs Particle/Field
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An Event: Higgs to 4 muons
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An Event: Higgs to 4 muons
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