P5 Science Drivers: Theory · P5 Science Drivers: Theory Stefan H oche SLAC National Accelerator...
Transcript of P5 Science Drivers: Theory · P5 Science Drivers: Theory Stefan H oche SLAC National Accelerator...
P5 Science Drivers: Theory
Stefan Hoche
SLAC National Accelerator Laboratory
DOE Exascale Requirements Review (HEP)
June 10, 2015
P5 recommendations
[http://www.usparticlephysics.org/p5]
From the summary:
I Specific investments in particle accelerator,instrumentation, and computing research and developmentare required to support the program and to ensurethe long-term productivity of the field.
From the report:
I Computing cuts across all activities in particle physics, and these activitiesspur innovation in computing. The field played leading roles in developingand using high-throughput and distributed/grid computing, online [..] dataprocessing, high-performance computing, high-performance networking,large-scale data storage, large-scale data management and analysis, and theWorld Wide Web [..]
Theory computations will continue to increase in importance, ashigher fidelity modeling will be required to understand the data.
1
Traditional HPC: Lattice QCD
I LQCD is only means to extract SMparameters depending onnon-perturbative dynamics of QCD
I Ab-initio calculation in discretespace-time with lattice spacings downto ∼ 0.06 fm in 1443 × 288 hypercube
I Systematic errors from continuumextrapolation and chiral extrapolation,the latter lately reduced and soonto be eliminated
2
Interplay with experiment
I Observables include masses,hadron decay properties andbasic Standard Model parameters
I Direct interpretation of BaBar, CLEO,CDF, DØ, Belle, LHCb, BESIII andBelle II experimental data
I Most precise determination of strongcoupling from LQCD, needed in searchfor new physics through Higgs-bosondecays at ATLAS & CMS
10.5 11.0 11.5 12.0 12.5mc/ms
HPQCD 0910.3102
ETMC 1010.3659
ETMC 1403.4504
MILC 1407.3772
HPQCD 1408 . 4169
Durr 1108.1650
u,d,s,c sea
u,d,s sea
u,d sea
[HPQCD ’14]
I Uncertainty reduction in theory predictions for muon g − 2may come from LQCD → would directly impact FNAL experiment
3
Interplay with experiment
jetsN
0 1 2 3 4 5 6 7
) [p
b]je
ts(W
+N
σ
-210
-110
1
10
210
310
410
510
610 ATLAS
jets, R=0.4,tanti-k
| < 4.4j
> 30 GeV, |yj
Tp
) + jetsν l→W(Data,
-1 = 7 TeV, 4.6 fbs+SHERPAATHLACKB
HEJALPGENSHERPAMEPS@NLO jetsN
0 1 2 3 4 5 6 7
Pre
d. /
Dat
a
0.6
0.8
1
1.2
1.4 +SHERPAATHLACKB
ATLAS
jetsN
0 1 2 3 4 5 6 7
Pre
d. /
Dat
a
0.6
0.8
1
1.2
1.4 HEJ
jetsN
0 1 2 3 4 5 6 7
Pre
d. /
Dat
a
0.6
0.8
1
1.2
1.4 ALPGEN
jetsN0 1 2 3 4 5 6 7
Pre
d. /
Dat
a
0.6
0.8
1
1.2
1.4
SHERPA
MEPS@NLO
I Both inclusive and fully differential results needed to scrutinize SM
I Particle-level predictions mandatory for direct comparison and unfolding
5
Perturbative QCD at the LHC
Aspects of the theory
I Perturbative regimeI Hard processesI Radiative corrections
I Non-perturbative regimeI HadronizationI Particle decays
Divide et Impera
I Quantity of interest: Total interaction rate
I Convolution of short & long distance physics
σp1p2→X =∑
i,j∈{q,g}
∫dx1dx2 fp1,i (x1, µ
2F )fp2,j (x2, µ
2F )︸ ︷︷ ︸
long distance
σij→X (x1x2, µ2F )︸ ︷︷ ︸
short distance
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pQCD Toolkit inventory
Current state of development
I Parton shower Monte Carlo (Herwig,Pythia,Sherpa,...)
I Automated NLO calculations(BlackHat,GoSam,Helac,MadLoop,MadGolem,NJet,OpenLoops,...)
I Matching to parton shower (aMC@NLO,Herwig,POWHEG Box,Sherpa,...)
I Merging of NLO calculations (aMC@NLO,Helac,Pythia,Sherpa,...)
Cutting edge technology & future directions
I Inclusive NNNLO (gg→H)
I Differential NNLO (V/H(+jet),γγ,VV,. . . )
I NNLO+NxLL resummation (gg→H,tt,. . . )
I NNLO+parton shower (W,Z,gg→H)
120
140
160
180
200
220
240
260
280
σto
t [p
b]
Scale variation
LO
NLONNLO
LL
NLLNNLL
LL NLLNNLL
LHC 8 TeV; mtop=173.3 GeV; A=0MSTW2008 LO; NLO; NNLO
Fixed OrderNLO+res
NNLO+res
tt cross section [Czakon et al.]
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Ultra-high precision calculations
10-1
100
101
dσ/dpjet
T[pb/GeV
]
W+ (→ lν) +1j, @ 8 TeV
LO
NLO
NNLO
40 60 80 100 120 140 160 180
p jetT [ GeV ]
0.6
1.0
1.4
1.8
2.2
K
NLO/LO
NNLO/NLO
[Boughezal,Focke,Liu,Petriello ’15]
I New method for regularizingdivergences (jettiness subtraction)
I Calculation performed usinghybrid MPI+OpenMP approach
LO NLO NNLO NNNLO
0
10
20
30
40
50
σ/pb
LHC
pp→h+X gluon fusion
MSTW08 68cl
μ=μR=μF ∈ [mH /4,mH ]
Central scale: μ = mH /2
2 4 6 8 10 12 14-0.2
-0.1
0.0
0.1
0.2
0.3
S /TeV
[Anastasiou,Duhr,Dulat,Herzog,Mistlberger ’15]
I First complete N3LO calculationat a hadron collider
I Total scale variation 3%, reducingtheory uncertainty by factor 3
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HPC usage projections from Snowmass 2013
Type of calculation CPU hours per project projects per year
NLO parton level 300,000 10-12Matrix Element Method 200,000 3-5
NNLO parton level 250,000 5-6Precision event generation 200,000 3Exclusive jet cross sections 300,000 1-2
Parton Distributions 50,000 5-6MSSM phenomenology 500,000 10
BSM constraints 150,000 2Model building 100,000 1-2
I Projected total of ≥6M CPUh for pQCD and ≥5.45M CPUh for BSM
I Prone to rapid changes depending on theory and technology developments
9
Actual HPC usage
Job Count by Number of Nodes
m1758 & m1738, Jun 2014 - Jun 2015
1024
512
256
128
64
32
16
8
4
2
1
Wall Hours by Number of Nodes
m1758 & m1738, Jun 2014 - Jun 2015
1024
512
256
128
64
32
16
8
4
2
1
I NERSC usage during past year ∼6.07M CPUh (pQCD only)
I Still at small-scale, but large potential for growth
I 7 publications in 2014, 3 in 2015 (as of Jun 8)
I First (full) calculation of W /H+jet at NNLO arXiv:1504.02131, arXiv:1505.03893
I First NNLO+PS matched simulation for Drell-Yan arXiv:1405.3607
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Technology development
threads used1 10 210
run
time
(sec
onds
)
1
10
PP-> H(->bb)+ 2 jets @ LO
Processor:
Intel Psi 5110P
AMD 6128 HE
Intel Xeon X5650
Intel Core i7-4770
PP-> H(->bb)+ 2 jets @ LO
threads used1 10 210
run
time
(sec
onds
)
210
310
PP-> H(->bb)+ 2 jets @ NLO
Processor:
Intel Psi 5110P
AMD 6128 HE
Intel Xeon X5650
Intel Core i7-4770
PP-> H(->bb)+ 2 jets @ NLO
I MCFM generator has been a workhorse in NLO calculations for years
I Recently thread- (OpenMP) and MPI-parallelized arXiv:1503.06182
I Used for jettiness subtraction at NNLO arXiv:1505.03893 and arXiv:1504.02131
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Summary
I Theory computing includes traditional and non-tradtional cases
I Lattice QCD has larger needs and well-developed technology
I Perturbative QCD is exploiting a large potential for growth
I BSM phenomenology still to join at larger scale (LBNL only so far)
I Small investments on computing can yield large returns on theory side(example pQCD NNLO W /Z+jet, computed at NERSC)