LHCb Accomplishments S. Stone 1 NSF, Nov. 5, 2013 & Future Physics.
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Transcript of LHCb Accomplishments S. Stone 1 NSF, Nov. 5, 2013 & Future Physics.
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LHCb Accomplishme
nts
S. Stone
1NSF, Nov. 5, 2013
& Future Physics
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The LHCb Collaboration 667 Authors
62 Institutes 16 Countries
4 Groups from USA
Basking in light of 2008 Nobel Prize to Kobayshi & Maskawa, “for the discovery of the origin of the broken symmetry which predicts the existence of at least 3 families of quarks”
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The LHCb Detector Complementary to ATLAS & CMS
Built to exploit correlated bb production
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q B (rad)q B (rad)
Production Of B vs B
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Detector
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f sensors
Rsensors
B-Vertex Measurement
Vertexing:• trigger on impact parameter• measurement of decay distance (time)
Ds
BsK
K
K
d~1cm
47 mm 144 mm
440 mmPrimary vertex
Decay time resolution = 40 fs
(s t) ~40 fs
Example: Bs → Ds K
Vertex Locator (Velo)Silicon strip detector with ~ 5 mm hit resolution 30 mm IP resolution
5NSF, Nov. 5, 2013
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Momentum and Mass measurement
Momentum meas. + direction (VELO): Mass resolution for background suppression
6NSF, Nov.
5, 2013
btag
Bs K
K
p+, K
Ds
Primary vertex
Bs→ Ds KMass resolutions ~15 MeV
Bo
m(DsK)
o - +
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NSF, Nov. 5, 2013
1 TeV Scale New Particles
Naturalness Higgs is most sensitive to physics of order M=125 GeV,
has been pushed to ~1 TeV due to absence of signals. Can be pushed higher. (Soni suggests 10 TeV for KK)
But corrections to Higgs mass go as M2, so can’t push M too high without getting into fine tuning problem
Need New Physics to cut off quantum corrections Suggested NP mechanisms: SUSY, Higgs
compositeness, and extra dimensions. Each predicts a rich spectrum of new states
7
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Seeking New Physics HFP as a tool for NP discovery
While measurements of fundamental constants are fun, the main purpose of HFP is to find and/or define the properties of physics beyond the SM
HFP probes large mass scales via virtual quantum loops. An example, of the importance of such loops is the Lamb shift in atomic hydrogen
A small difference in
energy between 2S1/2 & 2P1 /2
that should be of equal energy
at lowest order
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Flavor as a High Mass Probe
Already excluded ranges if ci~1 , take ci = 1
NSF, Nov. 5, 20139
i
See: Isidori, Nir& Perez arXiv:1002.0900; Neubert EPS 2011 talk
Ways out1. New particles have
large masses >>1 TeV
2. New particles have degenerate masses
3. Mixing angles in new sector are small, same as in SM (MFV)
4. The above already implies strong constrains on NP
New physics ruled outfrom Li=0 to somewherein the blue boxes
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NSF, Nov. 5, 2013
Limits on NP Higgs Yukawa’s (Harnik, Kopp & Zupan
arXiv:1209.1397)
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A few b decay results
“The success of the LHCb experiment has so far been a nightmare for all flavour physicists…” Gauld, Goetz and Haisch arXiv:1310:1082
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Dms from Bs→Ds
+p-
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CPV in Bs→J/ yX
CP violation means, for example, that a B will have a different decay rate than a B
Can occur via interference
between mixing & decay
For f =J/y f or J/y f0
Small CPV expected, good place for NP to appear
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background
f (980)peak, nowuse larger range
0
fs from Bs→J/yp+p-
f0 Mode predicted
by Stone & Zhang,
found by LHCb In region between
arrows, measured
to be >97.7%
CP-odd @95% cl
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fs results
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Combined LHCb values: =0.661±0.04 ±0.006 G(ps-1).
=0.106 ±0.011±0.007 DG (ps-1), fs=0.01±0.07±0.01 (rad)Indications of large fs from CDF/D0 not confirmed
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Bs→m+m- SM branching ratio is (3.2±0.2)x10-9 [Buras
arXiv:1012.1447], NP can make large contributions.
Many NP models possible, not just Super-Sym
16NSF, Nov. 5, 2013
Standard Model MSSM
~tan6b
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NSF, Nov. 5, 2013
Evidence for Bs→m+m-
17
BDT
BsBo
B→h+h-
B→pmn
B→pmm
3/fb
CMS 25/fb
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Fake D+
D+ Dfb
Prompt D+
LHCb
LHCb
D+→K-p+p+
Production fractions: B→DXmn
use equality of Gsl & known t’s
18NSF, Nov. 5, 2013
Ds→K-K+-p+
Ds
Also Do, Lb
Must know #Bs to measure B
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Also B→Dh-
LHCb measures
fs/fd=0.259±0.015 Used by CMS & ATLAS Pt dependence now
evident, CMS/ATLAS
implications
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D-p+
D-K+ Ds-p+
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Implications
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A sample of other results
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Electroweak Unique x-Q2
regions for structure function studies
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Central exclusive production
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J/y
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Publications
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Syracuseauthored~20% ofLHCbpapers
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LHCb Upgrade Can accumulate data ~x10 the rate in
hadronic channels, ~x5 in dimuon channels Relies on triggering at ~40 MHz without hard
wired cuts by using detached vertices Requires replacing all electronics except
calorimeter & muon, including rebuilding VELO, UT, TT & replacing RICH HPD’s
Allows us to extend range of mass probed for new physics by a significant factor
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Upgrade physics
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✓
✓= Syracuse analysis
✓
✓
✓
MIT
MIT
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Importance of the UT Use VELO-UT in trigger to improve
throughput (see M. Williams talk) Reduces ghosts in
tracking
Essential for KS reconstruction for decays after the VELO
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Conclusions LHCb is now sensitive to potential New Physics
effects at high mass scales We are searching for and limiting New Physics,
especially in rare and CP violating b & c decays In addition there are important research
directions in other areas: light meson structure qq versus tetraquark, exotic mesons, central exclusive production, electroweak physics….
The upgrade will allow much more sensitive searches in a variety of areas
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The End
29NSF, Nov. 5, 2013