Physics of the Large Hadron Collider - Durham...
Transcript of Physics of the Large Hadron Collider - Durham...
Why Hadron Colliders?
Discovery machines
W±, Z 0, t, H , . . .
Precision instruments
MW , mt , Bs oscillation frequency, . . .
Large energy reach · High event rate
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Why Hadron Colliders?
Explore a rich diversity of elementary processesat the highest accessible energies:
(qi , qi , g , . . .)⊗ (qi , qi , g , . . .)
Example: quark-quark collisions at√s = 1 TeV
If 3 quarks share half the proton’s momentum (〈x〉 = 16),
require pp collisions at√s = 6 TeV
; Fixed-target machine with beam momentump ≈ 2× 104 TeV = 2× 1016 eV (cf. cosmic rays).
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Cosmic-ray Spectrum
[eV]E
1310 1410 1510 1610 1710 1810 1910 2010
]-1
sr
-1 s
-2 m
1.6
[G
eVF
(E)
2.6
E
1
10
210
310
410
Grigorov
JACEE
MGU
Tien-Shan
Tibet07
Akeno
CASA-MIA
HEGRAFly’s Eye
Kascade
Kascade Grande 2011
AGASA
HiRes 1
HiRes 2Telescope Array 2011
Auger 2011
Knee
Ankle
dI
dE(2× 1016 eV) = (3 - 5)× 10−16 m−2 s−1 sr−1 eV−1
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How to achieve?
Fixed-target, p ≈ 2× 104 TeVRing radius is
r =10
3·( p
1 TeV
)/( B
1 tesla
)km.
Conventional copper magnets (B = 2 teslas) ;
r ≈ 13 × 105 km.
≈ 112 size of Moon’s orbit
10-tesla field reduces the accelerator to mere Earth size(R⊕ = 6.4× 103 km).
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Fermi’s Dream Machine (1954)
5000-TeV protons to reach√s ≈ 3 TeV
2-tesla magnets at radius 8000 km
Projected operation 1994, cost $170 billion(inflation assumptions not preserved)
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Key Advances in Accelerator Technology
Alternating-gradient (“strong”) focusing, invented byChristofilos, Courant, Livingston, and Snyder.
Before and After . . .
Synchrotron Beam Tube Magnet Size
Bevatron (6.2 GeV) 1 ft× 4 ft 912
ft× 2012
ft
FNAL Main Ring (400 GeV) ∼ 2 in× 4 in 14 in× 25 in
LHC (→ 7 TeV) 56 mm (SC)
The idea of colliding beams.
Superconducting accelerator magnets based on“type-II” superconductors, including NbTi and Nb3Sn.Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 6 / 54
Key Advances . . .
Active optics to achieve real-time corrections of theorbits makes possible reliable, highly tunedaccelerators using small-aperture magnets. Also“cooling,” or phase-space compaction of storedantiprotons.
The evolution of vacuum technology. Beams storedfor approximately 20 hours travel ∼ 2× 1010 km,about 150 times the Earth–Sun distance, withoutencountering a stray air molecule.
The development of large-scale cryogenic technology,to maintain many km of magnets at a few kelvins.
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Hadron Colliders through the Ages
CERN Intersecting Storage Rings: pp collider at√s → 63 GeV. Two rings of conventional magnets.
SppS Collider at CERN: pp collisions at√s = 630(→ 900) GeV in conventional-magnet SPS.
Fermilab Tevatron Collider: pp collisions at√s ≈ 2 TeV with 4-T SC magnets in a 2π-km tunnel.
Brookhaven Relativistic Heavy-Ion Collider: 3.45-Tdipoles in 3.8-km tunnel. Polarized pp,
√s → 0.5 TeV
Large Hadron Collider at CERN: 14-TeV pp collider inthe 27-km LEP tunnel, using 9-T magnets at 1.8 K.
High-energy collider parameters, 2012 Review of Particle Properties §28
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Large Hadron Collider at CERN
LHCb
ATLASALICE
CMS
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√s = 8 TeV Interaction Rates
extracted and applied as a function of the T2 track multi-plicity and affects only the 1h category. The systematicuncertainty is estimated to be 0.45% which correspondsto the maximal variation of the background that gives acompatible fraction of 1h events (trigger and pileup cor-rected) in the two samples.
Trigger efficiency: This correction is estimated from thezero-bias triggered events. It is extracted and applied as afunction of the T2 track multiplicity, being significantfor events with only one track and rapidly decreasing tozero for five or more tracks. The systematic uncertainty isevaluated comparing the trigger performances with andwithout the requirement of having a track pointing to thevertex and comparing the overall rate correction in the twosamples.
Pileup: This correction factor is determined from thezero-bias triggered events: the probability to have a bunchcrossing with tracks in T2 is 0.05–0.06 from which theprobability of having n 2 inelastic collisions with tracksin T2 in the same bunch crossing is derived. The systematicuncertainty is assessed from the variation, within the samedata set, of the probability to have a bunch crossing withtracks in T2 and from the uncertainty due to the T2 eventreconstruction efficiency.
Reconstruction efficiency: This correction is estimatedusing Monte Carlo generators (PYTHIA8 [13], QGSJET-II-03 [14]) tuned with data to reproduce the measuredfraction of 1h events which is equal to 0:216 0:007.The systematic uncertainty is assumed to be half of thecorrection: as it mainly depends on the fraction of eventswith only neutral particles in T2, it accounts for variationsbetween the different Monte Carlo generators.
T1 only: This correction takes into account the amountof events with no final state particles in T2 but one ormore tracks in T1. The uncertainty is the precision withwhich this correction can be calculated from the zero-biassample plus the uncertainty of the T1 reconstructionefficiency.
Internal gap covering T2: This correction takes intoaccount the events which could have a rapidity gap fullycovering the T2 range and no tracks in T1. It is estimatedfrom data, measuring the probability of having a gap in T1
and transferring it to the T2 region. The uncertainty takesinto account the different conditions (average chargedmultiplicity, pT threshold, gap size, and surroundingmaterial) between the two detectors.Central diffraction: This correction takes into account
events with all final state particles outside the T1 and T2pseudorapidity acceptance and it is determined from simu-lations based on the PHOJET and MBR event generators[15,16]. Since the cross section is unknown and the uncer-tainties are large, no correction is applied to the inelasticrate but an upper limit of 0.25 mb is taken as an additionalsource of systematic uncertainty.Low mass diffraction: The T2 acceptance edge at jj ¼
6:5 corresponds approximately to diffractive masses of3.6 GeV (at 50% efficiency). The contribution of eventswith all final state particles at jj> 6:5 is estimated withQGSJET-II-03 after tuning the Monte Carlo prediction with
TABLE IV. Summary of the measured cross sections with detailed uncertainty composition.The uncertainty follows from the COMPETE preferred-model extrapolation error of0:007. The right-most column gives the full systematic uncertainty, combined in quadratureand considering the correlations between the contributions.
Systematic uncertainty
Quantity Value el. t-dep el. norm inel ) full
tot (mb) 101.7 1:8 1:4 1:9 0:2 ) 2:9inel (mb) 74.7 1:2 0:6 0:9 0:1 ) 1:7el (mb) 27.1 0:5 0:7 1:0 0:1 ) 1:4el=inel (%) 36.2 0:2 0:7 0:9 ) 1:1el=tot (%) 26.6 0:1 0:4 0:5 ) 0:6
FIG. 1 (color). Compilation [8,20–24] of the total (tot), in-elastic (inel) and elastic (el) cross-section measurements: theTOTEM measurements described in this Letter are highlighted.The continuous black lines (lower for pp, upper for pp) repre-sent the best fits of the total cross-section data by the COMPETEcollaboration [19]. The dashed line results from a fit of theelastic scattering data. The dash-dotted lines refer to the inelasticcross section and are obtained as the difference between thecontinuous and dashed fits.
PRL 111, 012001 (2013) P HY S I CA L R EV I EW LE T T E R Sweek ending5 JULY 2013
012001-4
σtot (101.7± 2.9) mb
σinel (74.7± 1.7) mb
σel (27.1± 1.4) mb
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Collider Cross Sections
0.1 1 1010
-7
10-6
10-5
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10-3
10-2
10-1
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σσσσZZ
σσσσWW
σσσσWH
σσσσVBF
MH=125 GeV
WJS2012
σσσσjet
(ET
jet > 100 GeV)
σσσσjet
(ET
jet > √√√√s/20)
σσσσggH
LHCTevatron
eve
nts
/ s
ec f
or L
= 1
03
3 c
m-2s
-1
σσσσb
σσσσtot
proton - (anti)proton cross sections
σσσσW
σσσσZ
σσσσt
σ
σ
σ
σ
(( ((nb
)) ))
√√√√s (TeV)
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Standard-model Cross Sections
W Z WW Wt
[pb]
tota
lσ
1
10
210
310
410
510
-120 fb
-113 fb
-15.8 fb
-15.8 fb
-14.6 fb
-12.1 fb-14.6 fb
-14.6 fb
-11.0 fb
-11.0 fb
-135 pb
-135 pb
tt t WZ ZZ
= 7 TeVsLHC pp
Theory
)-1Data (L = 0.035 - 4.6 fb
= 8 TeVsLHC pp
Theory
)-1Data (L = 5.8 - 20 fb
ATLAS PreliminaryATLAS PreliminaryATLAS Preliminary
σtot ≈ 1011 pb
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Luminosity
Number N of events of interest
N = σ
∫dt L(t)
L(t): instantaneous luminosity [in cm−2 s−1]
Bunches of n1 and n2 particles collide head-on atfrequency f :
L(t) = fn1n2
4πσxσy
σx,y: Gaussian rms ⊥ beam sizes
Edwards & Syphers, 2012 Review of Particle Physics, §27LHC lumi calculator Zimmerman, “LHC: The Machine,” SSI 2012
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Exercise 1
(a) Estimate the integrated luminosity required to make aconvincing observation of each of the standard-model finalstates shown in the ATLAS plot above . Take into accountthe gauge-boson branching fractions given in the 2012Review of Particle Physics.
(b) Taking a nominal year of operation as 107 s, translateyour results into the required average luminosity.
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LHC Luminosity, 2012
Lpeak ≈ 7.7× 1033 cm−2 s−1 ATLAS & CMS
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Collider kinematics
Because of its properties under Lorentz boosts, rapidity,
y ≡ 12 ln
∣∣∣∣E + pzE − pz
∣∣∣∣,is a highly convenient longitudinal variable for anindividual particle or a jet. Pseudorapidity,
η ≡ − ln tan(θ?/2),
is a close approximation to y in the setting of colliderdetectors, and can be measured, even when the mass ofthe outgoing object is unknown.
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Exercise 2(a) Expand the definition
y ≡ 12 ln
∣∣∣∣E + pzE − pz
∣∣∣∣of rapidity for an object with mass m, under theassumption that p m, to show that as m/p → 0,
y → η ≡ − ln tan(θ?/2).
cf. 2012 Review of Particle Physics §43.5.2
(b) For pion production, compute the maximum c.m.rapidity at
√s = (8, 14) TeV and deduce the angular
coverage required to observe the full range.Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 17 / 54
Charged-particle density, η ≈ 0
Eur. Phys. J. C (2010) 68: 345–354 353
there is a large spread of values between different models:PHOJET is the lowest and PYTHIA tune Perugia-0 the high-est.
Fig. 2 Charged-particle pseudorapidity density in the central pseudo-rapidity region |η| < 0.5 for inelastic and non-single-diffractive colli-sions [4, 16–25], and in |η| < 1 for inelastic collisions with at leastone charged particle in that region (INEL > 0|η|<1), as a function ofthe centre-of-mass energy. The lines indicate the fit using a power-lawdependence on energy. Note that data points at the same energy havebeen slightly shifted horizontally for visibility
6 Conclusion
We have presented measurements of the pseudorapidity den-sity and multiplicity distributions of primary charged par-ticles produced in proton–proton collisions at the LHC, ata centre-of-mass energy
√s = 7 TeV. The measured value
of the pseudorapidity density at this energy is significantlyhigher than that obtained from current models, except forPYTHIA tune ATLAS-CSC. The increase of the pseudora-pidity density with increasing centre-of-mass energies is sig-nificantly higher than that obtained with any of the modelsand tunes used in this study.
The shape of our measured multiplicity distribution is notreproduced by any of the event generators considered. Thediscrepancy does not appear to be concentrated in a singleregion of the distribution, and varies with the model.
Acknowledgements The ALICE collaboration would like to thankall its engineers and technicians for their invaluable contributions to theconstruction of the experiment and the CERN accelerator teams for theoutstanding performance of the LHC complex.
The ALICE collaboration acknowledges the following fundingagencies for their support in building and running the ALICE detec-tor:
– Calouste Gulbenkian Foundation from Lisbon and Swiss FondsKidagan, Armenia;
– Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq), Financiadora de Estudos e Projetos (FINEP), Fundação deAmparo à Pesquisa do Estado de São Paulo (FAPESP);
Fig. 3 Measured multiplicity distributions in |η| < 1 for the INEL >
0|η|<1 event class. The error bars for data points represent statisticaluncertainties, the shaded areas represent systematic uncertainties. Left:The data at the three energies are shown with the NBD fits (lines).Note that for the 2.36 and 7 TeV data the distributions have beenscaled for clarity by the factors indicated. Right: The data at 7 TeV
are compared to models: PHOJET (solid line), PYTHIA tunes D6T(dashed line), ATLAS-CSC (dotted line) and Perugia-0 (dash-dottedline). In the lower part, the ratios between the measured values andmodel calculations are shown with the same convention. The shadedarea represents the combined statistical and systematic uncertainties
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Charged-particle multiplicity, |η| < 1
Eur. Phys. J. C (2010) 68: 345–354 353
there is a large spread of values between different models:PHOJET is the lowest and PYTHIA tune Perugia-0 the high-est.
Fig. 2 Charged-particle pseudorapidity density in the central pseudo-rapidity region |η| < 0.5 for inelastic and non-single-diffractive colli-sions [4, 16–25], and in |η| < 1 for inelastic collisions with at leastone charged particle in that region (INEL > 0|η|<1), as a function ofthe centre-of-mass energy. The lines indicate the fit using a power-lawdependence on energy. Note that data points at the same energy havebeen slightly shifted horizontally for visibility
6 Conclusion
We have presented measurements of the pseudorapidity den-sity and multiplicity distributions of primary charged par-ticles produced in proton–proton collisions at the LHC, ata centre-of-mass energy
√s = 7 TeV. The measured value
of the pseudorapidity density at this energy is significantlyhigher than that obtained from current models, except forPYTHIA tune ATLAS-CSC. The increase of the pseudora-pidity density with increasing centre-of-mass energies is sig-nificantly higher than that obtained with any of the modelsand tunes used in this study.
The shape of our measured multiplicity distribution is notreproduced by any of the event generators considered. Thediscrepancy does not appear to be concentrated in a singleregion of the distribution, and varies with the model.
Acknowledgements The ALICE collaboration would like to thankall its engineers and technicians for their invaluable contributions to theconstruction of the experiment and the CERN accelerator teams for theoutstanding performance of the LHC complex.
The ALICE collaboration acknowledges the following fundingagencies for their support in building and running the ALICE detec-tor:
– Calouste Gulbenkian Foundation from Lisbon and Swiss FondsKidagan, Armenia;
– Conselho Nacional de Desenvolvimento Científico e Tecnológico(CNPq), Financiadora de Estudos e Projetos (FINEP), Fundação deAmparo à Pesquisa do Estado de São Paulo (FAPESP);
Fig. 3 Measured multiplicity distributions in |η| < 1 for the INEL >
0|η|<1 event class. The error bars for data points represent statisticaluncertainties, the shaded areas represent systematic uncertainties. Left:The data at the three energies are shown with the NBD fits (lines).Note that for the 2.36 and 7 TeV data the distributions have beenscaled for clarity by the factors indicated. Right: The data at 7 TeV
are compared to models: PHOJET (solid line), PYTHIA tunes D6T(dashed line), ATLAS-CSC (dotted line) and Perugia-0 (dash-dottedline). In the lower part, the ratios between the measured values andmodel calculations are shown with the same convention. The shadedarea represents the combined statistical and systematic uncertainties
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Charged-particle spectrament follows this trend. The choice of the jj interval caninfluence the average pT value by a few percent.For jj< 0:5, the average charged multiplicity density
is dNch=d ¼ 5:78 0:01ðstatÞ 0:23ðsystÞ for NSDevents. The
ffiffiffis
pdependence of the measured dNch=
dj0 is shown in Fig. 5, which includes data from
various other experiments. The dNch=d results reportedhere show a rather steep increase between 0.9 and 7 TeV,which is measured to be ½66:1 1:0ðstatÞ 4:2ðsystÞ%.Using a somewhat different event selection, the ALICECollaboration has found a similar increase of ½57:60:4ðstatÞþ3:6
1:8ðsystÞ% [5]. The measured charged-particle
multiplicity is accurate enough to distinguish amongmost sets of event-generator tuning parameter values andvarious models. The measured value at 7 TeV significantlyexceeds the prediction of 4.57 from PHOJET [9,10], and thepredictions of 3.99, 4.18, and 4.34 from the DW [17],PROQ20 [18], and Perugia0 [19] tuning parameter values
of PYTHIA, respectively, while it is closer to the predictionof 5.48 from the PYTHIA parameter set from Ref. [8] and tothe recent model predictions of 5.58 and 5.78 fromRefs. [20,21]. The measured excess of the number ofcharged hadrons with respect to the event generators isindependent of and concentrated in the pT < 1 GeV=c
η-2 0 2
η/d
chdN
0
2
4
6
CMS NSD
ALICE NSD
UA5 NSD
0.9 TeV
2.36 TeV
7 TeV
CMS
FIG. 3. Distributions of dNch=d, averaged over the threemeasurement methods and compared with data from UA5 [23](p p, with statistical errors only) and ALICE [24] (with system-atic uncertainties). The shaded band shows systematic uncer-tainties of the CMS data. The CMS and UA5 data are averagedover negative and positive values of .
[GeV]s10 210 310 410
[GeV
/c]
⟩Tp⟨
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
ISR inel.
UA1 NSD
E735 NSD
CDF NSD
CMS NSD
s 2 + 0.00143 lns0.413 - 0.0171 ln
CMS
FIG. 4. Average pT of charged hadrons as a function of thecenter-of-mass energy. The CMS measurements are for jj<2:4. Also shown are measurements from the ISR [25] (pp), E735[26] (p p), and CDF [27] (p p) for jj< 0:5, and from UA1 [16](p p) for jj< 2:5. The solid line is a fit of the functional formhpTi ¼ 0:413 0:0171 lnsþ 0:001 43ln2s to the data. The errorbars on the CMS data include the systematic uncertainties.
[GeV]s10 210 310 410
0≈η η/d
chdN
0
1
2
3
4
5
6
7 UA1 NSD
STAR NSD
UA5 NSD
CDF NSD
ALICE NSD
CMS NSD
NAL B.C. inel.
ISR inel.
UA5 inel.
PHOBOS inel.
ALICE inel.
s 2 + 0.0267 lns2.716 - 0.307 ln
s 2 + 0.0155 lns1.54 - 0.096 ln
CMS
FIG. 5. Average value of dNch=d in the central region as afunction of center-of-mass energy in pp and p p collisions. Alsoshown are NSD and inelastic measurements from the NALBubble Chamber [28] (p p), ISR [29] (pp), UA1 [16] (p p),UA5 [23] (p p), CDF [30] (p p), STAR [31] (pp), PHOBOS [32](pp), and ALICE [24] (pp). The curves are second-order poly-nomial fits for the inelastic (solid) and NSD event selections(dashed). The error bars include systematic uncertainties, whenavailable. Data points at 0.9 and 2.36 TeV are slightly displacedhorizontally for visibility.
PRL 105, 022002 (2010) P HY S I CA L R EV I EW LE T T E R Sweek ending9 JULY 2010
022002-4
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PileupTypical LHC operation: 1.5× 1011 protons / bunch
bunch separation 50 ns
; multiple interactions / crossing
Mean Number of Interactions per Crossing0 5 10 15 20 25 30 35 40 45 50
/0.1
]-1
Rec
orde
d Lu
min
osity
[pb
0
20
40
60
80
100
120
140 =8 TeVsOnline 2012, ATLAS -1Ldt=20.8 fb0> = 20.7µ<
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Pileup: Z → µ+µ− in 25 interactions in ATLAS
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Pileup: 78 interactions in CMS
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Exercise 3
Consider the reaction p±p → jet1 + jet2 + anything atc.m. energy
√s. Denote the rapidity of the dijet system
as yboost ≡ 12(y1 + y2) and the individual jet rapidity in the
dijet rest frame as y ∗ ≡ 12(y1 − y2).
(a) Neglecting the invariant masses of the individual jetswith respect to p⊥, show that the invariant mass of thedijet system, and thus of the colliding partons, is√s = 2p⊥ cosh y ∗.
(b) Deduce the momentum fractions carried by the twocolliding partons. Show that xa,b =
√τe±yboost, where
τ ≡ s/s.
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ATLAS
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CMS (Compact Muon Solenoid)
SUPERCONDUCTING SOLENOIDNiobium titanium coil carrying ~18,000A
PRESHOWERSilicon strips ~16m! ~137,000 channels
SILICON T!CKERSPixel (100x150 μm) ~16m! ~66M channelsMicrostrips (80x180 μm) ~200m! ~9.6M channels
MUON CHAMBERSBarrel: 250 Dri" Tube, 480 Resistive Plate ChambersEndcaps: 468 Cathode Strip, 432 Resistive Plate Chambers
FORWARD CALORIMETERSteel + Quartz #bres ~2,000 Channels
STEEL RETURN YOKE12,500 tonnes
HADRON CALORIMETER (HCAL)Brass + Plastic scintillator ~7,000 channels
CRYSTAL ELECTROMAGNETICCALORIMETER (ECAL)~76,000 scintillating PbWO! crystals
Total weightOverall diameterOverall lengthMagnetic "eld
: 14,000 tonnes: 15.0 m: 28.7 m: 3.8 T
CMS DETECTOR
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LHCb
14 AAAS, 2011 First physics from the LHC Monica Pepe Altarelli Studying beauty at LHCb
pp collision Point
Vertex Locator
VELO
Tracking System
Muon System RICH Detectors
Calorimeters
• ~ 1 cm
• B
Movable device
35 mm from beam out of physics /
7 mm from beam in physics
LHCb
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ALICE
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ALICE (Pb–Pb event)
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Computing Cross Sections: factorization
i √s
a b
j_
σ
ˆ
dσ
dy1dy2dp⊥=∑i j
2πp⊥(1 + δij)s
[f(a)i (xa, s)f
(b)j (xb, s)σij(s, t, u) + (i ↔ j)
]. . . + fragmentation (partons → particles)
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What Is a Proton?
(For hard scattering) a broad-band, unselected beam ofquarks, antiquarks, gluons, & perhaps other constituents,characterized by parton densities
f(a)i (xa,Q
2),
. . . number density of species i with momentum fractionxa of hadron a seen by probe with resolving power Q2.
Q2 evolution given by QCD perturbation theory
f(a)i (xa,Q
20): nonperturbative
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Asymptotic Freedom1
αs(Q)=
1
αs(µ)+
(33− 2nf)
6πln
(Q
µ
)
100 101 102 103
Q [GeV]
2
3
4
5
6
7
8
9
10
11
121/α s
Group: 1Group: 2Group: 16Group: 5Group: 6Group: 7Group: 8Group: 9Group: 10Group: 11Group: 12Group: 13Group: 14Group: 29
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QCD Tests: e+e− → hadrons
10-1
1
10
10 2
10 3
1 10 102
R
ω
ρ
φ
ρ
J/ψ ψ (2S)Υ
Z
√s [GeV]
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QCD Tests: Quark Confinement
-4
-3
-2
-1
0
1
2
3
0.5 1 1.5 2 2.5 3
[V(r)
-V(r 0
)] r 0
r/r0
β = 6.0β = 6.2β = 6.4Cornell Potential
0
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Deeply Inelastic Scattering ; f(a)i (xa,Q
20 )
107
106
105
104
103
102
10
1
10–1
10–2
10–3
Q2 (GeV2)
σ r (x
,Q2 )
NC
102 103 104 10510
x=6.18•10–5
x=9.5•10–5
x=2•10–4
x=3.2•10–4
x=5•10–4
x=8•10–4
x=1.3•10–3
x=2•10–3
x=3.2•10–3
x=5•10–3
x=8•10–3
x=1.3•10–2
x=0.015 (x40)
x=0.045 (x12)
x=0.08 (x6)
x=0.125 (x3.5)
x=0.175 (x2)
x=0.225 (x1.5)
x=0.275 (x1.2)
x=0.35
x=0.45
x=0.55
x=0.65
x=0.75
NuTeVCCFR 97CDHSWNuTeV fit
x=2•10–2
x=3.2•10–2
x=5•10–2
x=8•10–2
x=0.13x=0.18
x=0.25
x=0.4
x=0.65
10
1
0.1
xF3(x
,Q2 )
Q2 (GeV2)100101
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 35 / 54
Parton Distribution Functions fi(x ,Q2)
x-410 -310 -210 -110 1
)2xf
(x,Q
0
0.2
0.4
0.6
0.8
1
1.2
g/10
d
d
u
uss,
cc,
2 = 10 GeV2Q
x-410 -310 -210 -110 1
)2xf
(x,Q
0
0.2
0.4
0.6
0.8
1
1.2
x-410 -310 -210 -110 1
)2xf
(x,Q
0
0.2
0.4
0.6
0.8
1
1.2
g/10
d
d
u
u
ss,
cc,
bb,
2 GeV4 = 102Q
x-410 -310 -210 -110 1
)2xf
(x,Q
0
0.2
0.4
0.6
0.8
1
1.2
MSTW 2008 NLO PDFs (68% C.L.)
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 36 / 54
Example reaction: quark–quark scattering
μ ig_2
– λaαβ γμ
β
α
a
σ(ud → ud) =4πα2
s
9s2· s
2 + u2
t2
; dσ/dΩ∗ ∝ 1/ sin4(θ∗/2)
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 37 / 54
Exercise 4
(a) Express the ud → ud cross section in terms of c.m.angular variables, and verify that the angular distributionis reminiscent of that for Rutherford scattering.
(b) In the search for new interactions, the angulardistribution for quark-quark scattering, inferred from dijetproduction in p±p collisions, is a sensitive diagnostic.Show that when re-expressed in terms of the variableχ = (1 + cos θ∗)/(1− cos θ∗), the angular distribution forud scattering is dσ/dχ ∝ constant.
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 38 / 54
Compositeness search in CMS (|yboost| < 1.11)
JHEP05(2012)055
dijetχ
2 4 6 8 10 12 14 16
dije
tχ
/ddi
jet
σ d
dije
tσ
1/
0.1
0.2
0.3
0.4
0.5
0.6
0.7
> 3.0 TeVjjM (+0.5)
< 3.0 TeVjjM2.4 < (+0.4)
< 2.4 TeVjjM1.9 < (+0.3)
< 1.9 TeVjjM1.5 < (+0.25)
< 1.5 TeVjjM1.2 < (+0.2)
< 1.2 TeVjjM1.0 < (+0.15)
< 1.0 TeVjjM0.8 < (+0.1)
< 0.8 TeVjjM0.6 < (+0.05)
< 0.6 TeVjjM0.4 <
CMS = 7 TeVs
-1L = 2.2 fb
DataQCD prediction
= 7 TeV (NLO)+LL/RRΛ
Figure 1. Normalized dijet angular distributions for |yboost| < 1.11 in several Mjj ranges. For
clarity, the distributions are shifted vertically by the additive amounts shown in parentheses in
the figure. The vertical error bars represent the statistical and systematic uncertainties added in
quadrature. The horizontal bars correspond to the χdijet bin width. The results are compared with
the predictions of NLO QCD with CTEQ6.6 PDF (shaded band) and with predictions for QCD+CI
from [12] at the CI scale Λ+LL/RR = 7 TeV (dashed histogram). Non-perturbative corrections due
to hadronization and multiple parton interactions are applied to the predictions. The shaded band
indicates the total uncertainty on the NLO QCD predictions due to µr and µf scale variations,
PDFs, as well as the uncertainties from the non-perturbative corrections, which have all been
added in quadrature.
certainties are represented by nuisance parameters which affect the χdijet distribution. The
nuisance parameters are varied within their Gaussian uncertainties when generating the
distributions of q. The QCD+CI model is considered to be excluded at the 95% confidence
– 7 –
χdijet = e |y1−y2|
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 39 / 54
Parton Luminosity
Hard scattering: σ ∝ 1/s; Resonance: σ ∝ τ ; form
τ
s
dLdτ≡ τ/s
1 + δij
∫ 1
τ
dx
x[f
(a)i (x)f
(b)j (τ/x) + f
(a)j (x)f
(b)i (τ/x)]
[dimensions σ] measures parton ij luminosity (τ = s/s)
σ(s) =∑i j
∫ 1
τ0
dτ
τ· τs
dLij
dτ· [sσij(s)]
Dmensionless factor [· · · ] ≈ determined by couplings.Logarithmic integral typically gives a factor of order unity.
My luminosity page Stirling luminosities
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 40 / 54
Parton Luminosity: gg
10-2 10-1 100 10110-610-510-410-310-210-1100101102103104105106
Parto
n Lu
min
osity
[nb]
0.9 TeV2 TeV4 TeV6 TeV7 TeV
10 TeV14 TeV
8 TeV
CTEQ6L1: gg
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 41 / 54
Parton Luminosity: ud
10-2 10-1 100 10110-610-510-410-310-210-1100101102103104105106
Parto
n Lu
min
osity
[nb]
0.9 TeV2 TeV
4 TeV6 TeV7 TeV
10 TeV14 TeV
Tevatron
8 TeV
[TeV]
CTEQ6L1: ud—
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 42 / 54
Parton Luminosity (light quarks)
10-2 10-1 100 10110-610-510-410-310-210-1100101102103104105106
Parto
n Lu
min
osity
[nb]
0.9 TeV2 TeV4 TeV6 TeV7 TeV8 TeV10 TeV14 TeV
CTEQ6L1: qq
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 43 / 54
Parton Luminosity: gq
10-2 10-1 100 10110-610-510-410-310-210-1100101102103104105106
Parto
n Lu
min
osity
[nb]
0.9 TeV2 TeV4 TeV6 TeV7 TeV8 TeV10 TeV14 TeV
CTEQ6L1: gq
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 44 / 54
Luminosity Ratios: gg
10-2 10-1 100 10110-3
10-2
10-1
100R
atio
to 1
4 Te
V
R.9R2R4R6R7
R10R8
CTEQ6L1: gg
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 45 / 54
Luminosity Ratios: ud
10-2 10-1 100 10110-3
10-2
10-1
100R
atio
to 1
4 Te
V
R0.9R2RTevR4R6R7
R10R8
CTEQ6L1: ud—
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 46 / 54
Luminosity Ratios (light quarks)
10-2 10-1 100 10110-3
10-2
10-1
100R
atio
to 1
4 Te
V
R0.9R2R4R6R7
R10R8
CTEQ6L1: qq
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 47 / 54
Luminosity Ratios: gq
10-2 10-1 100 10110-3
10-2
10-1
100R
atio
to 1
4 Te
V
R0.9R2R4R6R7R8R10
CTEQ6L1: gq
[TeV]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 48 / 54
Luminosity Contours: gg
2 103 4 5 6 7 8[TeV]
0.1
1
10
0.20.30.40.5
2345
[TeV
] 0.1 pb1 pb10 pb100 pb1 nb10 nb
CTEQ6L1: gg
14
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 49 / 54
Luminosity Contours: ud
2 103 4 5 6 7 8[TeV]
0.1
1
10
0.20.30.40.5
2345
[TeV
] 0.1 pb1 pb10 pb100 pb1 nb10 nb
CTEQ6L1: ud—
14
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 50 / 54
Luminosity Contours (light quarks)
2 103 4 5 6 7 8[TeV]
0.1
1
10
0.20.30.40.5
2345
[TeV
]
0.1 pb1 pb10 pb100 pb1 nb10 nb
CTEQ6L1: qq
14
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 51 / 54
Luminosity Contours: gq
2 103 4 5 6 7 80.1
1
10
0.20.30.40.5
2345
0.1 pb1 pb10 pb100 pb1 nb10 nb
CTEQ6L1: gq
[TeV]14
[TeV
]
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 52 / 54
Venerable OverviewSupercollider physics
E. Eichten
Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510
I. Hinchliffe
Lawrence Berkeley Laboratory, Berkeley, California 94720
K. Lane
The Ohio State University, Columbus, Ohio 43210
C. Quigg
Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois 60510
Eichten et al. summarize the motivation for exploring the 1-TeV (= tol2 eV) energy scale in elementary particle interactions and explore the capabilities of proton-(anti)proton colliders with beam energies between 1 and 50 TeV. The authors calculate the production rates and characteristics for a number of conventional processes, and discuss their intrinsic physics interest as well as their role as backgrounds to more exotic phenomena. The authors review the theoretical motivation and expected signatures for several new phenomena which may occur on the 1-TeV scale. Their results provide·a reference'point for the choice of machine parameters and for experiment design.
CONTENTS 1. Gaugino pair production 668
I. Introduction A. Where we stand B. The importance of the 1-TeV scale c. The purpose and goals of this paper
II. Preliminaries A. Parton model ideas B. Q2-dependent parton distributions c. Parton-parton luminosities
III. Physics of Hadronic Jets A: Generalities B. Two-jet final states c. Multijet phenomena D. Summary
IV. Electroweak Phenomena A. Dilepton production B. Intermediate boson production c. Pair production of gauge bosons
1. Production of w+ w- pairs 2. Production of w±zo pairs 3. Production of Z 0Z 0 pairs 4. w±r production 5. Z 0y production
D. Production of Higgs bosons E. Associated production of Higgs bqsons and gauge
bosons F. Summary
v. Minimal ExtenSions of the Standard Model A. Pair production of heavy quarks B. Pair production of heavy leptons c. New electroweak gauge bosons D. Summary
VI. Technicolor A. Motivation B. The minimal technicolor model c. The Farhi-Susskind model D. Single production of technipions E. Pair production of technipions F. Summary
VII. Supersymmetry A. Superpartner spectrum and elementary cross
sections
Reviews of Modern Physics. Vol. 56, No.4, October 1984
579 580 581 582 583 583 585 592 596 596 598 607 617 617 618 621 624 625 628 630 631 632 633
640 642 642 643 645 648 650 650 650 652 655 660 662 665 666
667
2. Associated production of squarks and gauginos 669 3. Squark pair production 670
B. Production and detection of strongly interacting superpartners 672
C. Production and detection of color singlet super-partners 676
D. Summary 683 VIII. Composite Quarks and Leptons 684
A. ~aD.ifestations of compositeness 685 B. Signals for compositeness in high-p1 jet production 687 C. Signals for composite quarks and leptons in lepton-
pair production 690 D. Summary 695
IX. Summary and Conclusions 696 Acknowledgments 698 Appendix. Parametrization& of the Parton Distribuiions 698 References 703
I. INTRODUCTION
The physics of elementary particles has undergone a remarkable development during the past decade. A host of new experimental results made accessible by a new generation of particle accelerators and the accompanying ra-. pid convergence of theoretical ideas have brought to the subject a new coherence. Our current outlook has been shaped by the identification of quarks and leptons as fundamental constituents of matter and by the gauge theory synthesis of the fundamental interactions. 1 These developments represent an important simplification of
1For expositions of the current paradigm, see the textbooks by Okun (1981), Perkins (1982), Aitchison and Hey (1982), Leader and Predazzi (1982), Quigg (1983), and Halzen and Martin (1984) and the summer school proceedings edited by Gaillard and Stora (1983).
Copyright @ 1984 The American Physical Society 579
Chris Quigg (FNAL) LHC Physics . . . Invisibles · 10–15.7.2013 53 / 54
Anticipating the LHC . . .
ANRV391-NS59-21 ARI 17 September 2009 18:15
Unanswered Questions in theElectroweak TheoryChris QuiggTheoretical Physics Department, Fermi National Accelerator Laboratory, Batavia, Illinois 60510
Institut fur Theoretische Teilchenphysik, Universitat Karlsruhe, D-76128 Karlsruhe, Germany
Theory Group, Physics Department, CERN, CH-1211 Geneva 23, Switzerland
Annu. Rev. Nucl. Part. Sci. 2009. 59:505–55
First published online as a Review in Advance onJuly 14, 2009
The Annual Review of Nuclear and Particle Scienceis online at nucl.annualreviews.org
This article’s doi:10.1146/annurev.nucl.010909.083126
Copyright c© 2009 by Annual Reviews.All rights reserved
0163-8998/09/1123-0505$20.00
Key Words
electroweak symmetry breaking, Higgs boson, 1-TeV scale, Large HadronCollider (LHC), hierarchy problem, extensions to the Standard Model
AbstractThis article is devoted to the status of the electroweak theory on the eveof experimentation at CERN’s Large Hadron Collider (LHC). A compactsummary of the logic and structure of the electroweak theory precedes an ex-amination of what experimental tests have established so far. The outstandingunconfirmed prediction is the existence of the Higgs boson, a weakly inter-acting spin-zero agent of electroweak symmetry breaking and the giver ofmass to the weak gauge bosons, the quarks, and the leptons. General argu-ments imply that the Higgs boson or other new physics is required on the1-TeV energy scale.
Even if a “standard” Higgs boson is found, new physics will be implicatedby many questions about the physical world that the Standard Model cannotanswer. Some puzzles and possible resolutions are recalled. The LHC movesexperiments squarely into the 1-TeV scale, where answers to important out-standing questions will be found.
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