2011 QCD and High Energy Interactions - Rencontres de Moriond ...

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ALEPH 91 - 206 GeV Event Shapes JADE 14 - 44 GeV Event Shapes ALEPH 91 - 206 GeV Event Shapes ALEPH 91 GeV Three Jet Rate OPAL 91 - 206 GeV Event Shapes World Average α S =0.1184±0.0007 Bethke, Eur. Phys. J. C64, 689 (2009) NNLO NNLO NNLO+NLLA NNLO+NLLA NNLO NLLO NLLO+NLLA 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15 0.16 0.17 αS (MZ ) Figure 2: The combined value of the strong coupling αS compared to similar measurements also using NLLO and matched NLLO+NLLA calculations. The yellow band indicates the world average of the strong coupling αS. e + e − -data do exist. The value obtained using τ-decays or applying a fit to electroweak precision observables result in a smaller overall uncertainty compared to this measurement 8 . Besides a precise determination of a fundamental parameter of the Standard Model this measurement can be seen as a consistency check of the theory of strong interactions, Quantum Chromo Dynamics. Acknowledgments This research was supported by the DFG cluster of excellence ’Origin and Structure of the Universe’. References 1. A. Gehrmann-De Ridder, T. Gehrmann, E.W.N. Glover, G. Heinrich, JHEP 12, 094 (2007). 2. S. Weinzierl, Phys. Rev. Lett. 101, 162001 (2008). 3. The OPAL Collaboration, hep-ex 1101.147v1, submitted to Eur. Phys. J. C. 4. S. Bethke et al., Eur. Phys. Jour. C 64, 351 (2009). 5. G. Dissertori it et al., JHEP 02, 040 (2008). 6. G. Dissertori it et al., JHEP 08, 036 (2009). 7. G. Dissertori it et al., Phys. Rev. Lett. 104, 072002 (2010). 8. S. Bethke, Eur. Phys. Jour. C 64, 689 (2009).
Reaching beyond NLO in processes with giant K-factors S. SAPETA LPTHE, UPMC Univ. Paris 6 and CNRS UMR 7589 Paris, France We present a method, called LoopSim, which allows one to obtain approximate higher order perturbative predictions for observables which exhibit large, kinematically induced NLO corrections. The approach makes use of combining NLO results for different multiplicities. We validate the method against known NNLO results for Drell-Yan lepton pt spectra and then we use it to compute approximate NNLO results for Z+jet observables. We also study dijet events and show that LoopSim can provide useful information even in cases without giant K-factors. 1 Introduction Next-to-leading order accuracy of QCD predictions has become a standard for processes calculated for the LHC. Most results show good convergence at NLO with corrections of the order of 10-20%. There are however cases of distributions which show very large K-factors from LO to NLO. One such example is inclusive Z+j production. At LO, the distributions of the transverse momentum of the Z-boson, pt,Z, the transverse momentum of the hardest jet, pt,j1, and the scalar sum of transverse momenta of all jets HT,jets are identical. This is because, as shown in the left diagram of Fig. 1, there are only two particles in the final state: the Z-boson and the parton and therefore their transverse momenta balance each other. At NLO, however, each of these distributions looks very different. While pt,Z spectrum is only slightly higher than at LO, the hadronic observables, pt,j1 and HT,jets, receive very large corrections that grow with pt and correspond to K-factors of 4 − 6 and 50 − 100, respectively. The reason is that most of the correction to pt,Z spectra at high values of transverse momenta comes from the NLO diagram which preserves LO topology, i.e. the Z-boson the leading jet are back-to-back as depicted in the middle diagram of Fig. 1. For hadronic observables, however, it is not important whether the Z-boson is hard or soft and the dominant topology turns out to be that of dijet type (right diagram of Fig. 1). Integration over soft and collinear emissions of the Z-boson leads to double logarithmic enhancement, which produces the large K-factors for pt,j1 and HT,jets distributions. For the HT,jets observable the enhancement is even bigger because the dijet topology leads to HT,jets ∼ 2pt,j1 instead of HT,jets = pt,j1 at LO. Hence, even though the pt,j1 and HT,jets distributions for Z+j are formally NLO they are, in some sense, leading contributions. This may raise some doubts about the accuracy of those predictions. Ideally, one would like to calculate the full NNLO corrections for Z+j to see if the convergence is restored. This result is however not yet available, the main difficulty being a proper combination of the tree and the 1-loop diagrams (i.e. Z+2j at NLO) with the 2-loop
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2011 QCD and High Energy Interactio
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Proceedings of the XLVIth RENCONTRE
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2011 RENCONTRES DE MORIOND The XLVI
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Foreword Contents 1. Higgs Searches
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1. Higgs
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95% CL Limit/SM 10 1 Tevatron Run I
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Events/5 GeV 6 10 5 10 4 10 3 10 2
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Events / 0.5 CDF Run II Preliminary
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For the most sensitive sub-channel
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Table 1: Table listing the various
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various SM Higgs mass hypotheses. T
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constraints on parameters are given
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Figure 2: Invariant mass of the ele
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Figure 4: CDF Exclusion limits for
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Table 1: Main phases of 2010 commis
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Table 4: Parameter list for early (
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luminosity of 1.2×10 33 cm −2 s
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2 QCD Analysis settings HERA PDFs a
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min 2 - 2 20 15 10 5 0 H1 and ZEUS
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SM σ / σ 95% CL Limit on 3 10 2 1
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NNLO σ/ σSM 95% CL Upper Bound on
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the report of this working group. I
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2.3 The impact of different PDF par
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SUSY Searches at the Tevatron Ph. G
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on the quality (loose or tight) and
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SUSY searches at ATLAS N. Barlow, o
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channel. These results are combined
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Figure 2: The top left plot shows t
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2010 data. Analysis techniques for
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as main discriminator between event
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sign leptons is particularly intere
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N of events 5 10 DATA 10 4 3 10 10
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) [pb] ν e → B(W’ × σ 10 1 -
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2 Searches in the dijet final state
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ing that the neutrinos were the onl
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The Quasi-Classical Model in SU(N)
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g (γ µ kµ) γ µ Aa µ g (pk)
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3. Top
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of their vertex with respect to the
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of about 9%. 3.1 Differential Cross
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Figure 5: Summary of most recent CD
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the minimum number of jets identifi
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where f’s are probability functio
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hood technique, with a simultaneous
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momentum direction of the b quark f
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Events 200 150 100 50 -1 DØ L=5.4
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after all corrections in the M t¯t
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for prompt J/ψ under the fully tra
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2 Events / 20 MeV/c 50 40 30 20 10
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ATLAS - consists of four parts (mon
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5 D mesons High cross-sections of D
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μ +X') [nb/GeV] → b+X → (pp T
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GeV) μ |
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HEAVY FLAVOUR IN A NUTSHELL Robert
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Figure 1: Overlapping constraints o
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Figure 3: Constraints on new physic
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RECENT B PHYSICS RESULTS FROM THE T
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(IP) distributions are fitted separ
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decays CDF extracts Using a 5.94 fb
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Search for B 0 s → µ+ µ − and
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Ref. 10,11 . The expected GL distri
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IN PURSUIT OF NEW PHYSICS WITH B DE
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τK + K −/τBs 1.01 1.00 0.99 0.9
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CHARMLESS HADRONIC B-DECAYS AT BABA
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surements (fL ∼ 0.5). Several att
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Estimating the Higher Order Hadroni
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the resulting exponent suggests to
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The counterpart of the ground-state
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(a) Tree level signal decay b ¯Bs
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the B0 d system LHCb profits from i
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This result is based on averaging o
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y non-perturbative effects. Using t
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e M(Dπ) distributions obtained D +
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CHARM PHYSICS RESULTS AND PROSPECTS
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LHCb is working towards its first m
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Two body hadronic D decays Yu Fushe
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where the effective coefficients aA
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6. J. J. Sakurai, Phys. Rev. 156, 1
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states: 6π, 2K4π, 4K2π, KSK3π 1
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egion of X(3872), which corresponds
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Figure 1: The π 0 recoil mass spec
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η → π + π − π 0 η ′ →
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conservation. This second principle
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many of them come from gluon nonper
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Latest Jets Results from the Tevatr
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in for the inclusive trijet event s
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RECENT RESULTS ON JETS FROM CMS F.
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dy (pb/GeV) /dp 2 d 10 10 10 9 10
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RECENT RESULTS ON JETS WITH ATLAS G
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| y| < 0.3 ATLAS Preliminary 2.1 <
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EPOS 2 and LHC Results TanguyPierog
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positions are randomly distributed
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ABOUT THE HELIX STRUCTURE OF THE LU
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Page 199 and 200: Improving NLO-parton shower matched
Page 201 and 202: due to the inclusion of higher orde
Page 203 and 204: New Results in Soft Gluon Physics C
Page 205 and 206: Figure 2: Spacetime depiction of Dr
Page 207 and 208: Central Exclusive Meson Pair Produc
Page 209 and 210: in the CEP cross section. However i
Page 211 and 212: AN AVERAGE b-QUARK FRAGMENTATION FU
Page 213 and 214: 1/N dN/dx 3.5 3 2.5 2 1.5 1 0.5 ALE
Page 215 and 216: W + W + jj at NLO in QCD: an exotic
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Page 219 and 220: W/Z+Jets and W/Z+HF Production at t
Page 221 and 222: Figure 2: Measured inclusive jet di
Page 223 and 224: W and Z physics with the ATLAS dete
Page 225 and 226: SHERPA 9 MC generators but not by P
Page 227 and 228: W/Z + Jets results from CMS V. CIUL
Page 229 and 230: Events / 0.1 600 500 400 300 200 10
Page 231 and 232: TEVATRON RESULTS ON MULTI-PARTON IN
Page 233 and 234: iterative midpoint cone algorithm w
Page 235 and 236: INVESTIGATIONS OF DOUBLE PARTON SCA
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Page 239 and 240: Figure 4: Two-dimensional distribut
Page 241 and 242: SOFT QCD RESULTS FROM ATLAS AND CMS
Page 243 and 244: as a function of multiplicity for t
Page 245 and 246: Determination of αS using hadronic
Page 247: α S (m Z 0) 0.15 0.14 0.13 0.12 0.
Page 251 and 252: dσ/dp t,max [fb/GeV] 10 5 10 4 10
Page 253 and 254: Nonlocal Condensate Model for QCD S
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Page 257 and 258: AN ALTERNATIVE SUBTRACTION SCHEME F
Page 259 and 260: where MBorn,g is the underlying Bor
Page 261 and 262: THE NNPDF2.1 PARTON SET F. CERUTTI
Page 263 and 264: ottom masses mb of 4.25, 4.5, 5.0 a
Page 265 and 266: HOLOGRAPHIC DESCRIPTION OF HADRONS
Page 267 and 268: ∫ SYM = κ d 4 ( 1 xdzTr 2 h(z)F
Page 269 and 270: Nuclear matter and chiral phase tra
Page 271 and 272: fact that for Nc ≫ 3 a gas of fre
Page 273 and 274: Recent Results on Light Hadron Spec
Page 275 and 276: Figure 3: Mass spectrum fitting wit
Page 277 and 278: MEASUREMENT OF THE J/ψ INCLUSIVE P
Page 279 and 280: 2 Counts per 40 MeV/c 120 100 80 60
Page 281 and 282: STUDY OF Ke4 DECAYS IN THE NA48/2 E
Page 283 and 284: photons were accepted while particl
Page 285: 6. Structure Functions Diffraction
Page 288 and 289: 2 Hadronic Final States and Diffrac
Page 290 and 291: 3 Summary A brief overview of recen
Page 293 and 294: Using HERA Data to Determine the In
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Page 297: The singular term, on the other han
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Pomeron Kernel: The leading order B
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DIFFRACTION, SATURATION AND pp CROS
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In Ref. 6 , the saturated Froissart
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Transverse Energy Flow with Forward
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1/N d dE t /dη 0.1 0.09 0.08 0.07
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7. Heavy Ions
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dη)/(0.5〈 N 〉 ) part ch (dN 10
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) 3 (fm long R side R out R 400 350
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correlation density is computed as
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Away-side gaussian width 1.4 1.2 1
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Figure 1: (a) J/ψ rapidity distrib
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lower x, or forward rapidity one ex
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φ ∆ /d assoc dN trig 1/N 0.5 0.4
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AA,Pythia I 2.5 2.0 1.5 1.0 0.5 0.0
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(1/N ) dN/dA evt J φ Δ ) dN/d (1/
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[GeV] Tower ET Σ 50 45 40 35 30 25
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3 Results 3.1 Dijet Properties in p
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(GeV/c) (GeV/c) T T p < 40 20
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wheredσm(N +N → h+X)/dp Tdy isth
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R AA 0.6 0.5 0.4 0.3 0.2 0.1 0 0.5
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Here D is the diffusion coefficient
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The effect of triangular flow in je
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When both trigger and associated pa
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The first Z boson measurement in th
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Figure 1: Dimuon invariant mass spe
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2. V. Kartvelishvili, R. Kvatadze a
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esolution [ µ m] ! r 0 d 300 250 2
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Figure 5: Differential transverse m
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Figure 1: Average nuclear modificat
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Another way of using direct photons
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Pb R g 2 Nuclear Modifications for
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q T 1/R AA 1.6 1.4 1.2 1 0.8 LO Fra
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] 2 > [g/cm max
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Methods (a) and (c) constrain the e
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EXPERIMENTAL SUMMARY: ENTERING THE
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ut also for valence quarks involved
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The sensitivity to Standard Model H
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Figure 10: Top pair mass spectrum m
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Figure 13: Particle densities (left
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4 Low energy precision Spectroscopy
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asymmetries associated to Bd and Bs
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XLVIth Rencontres de Moriond QCD an
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