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

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Figure 1: Rapidity of the vector boson (left) and pT spectrum of the second jet (right) in W boson production at the LHC. Blue histograms show the Menlops predictions, while Nlops and Meps predictions are depicted as red circles and green crosses, respectively. σ PW/ME (j) denoting the cross section for producing j jets in the Powheg / Meps methods. The limit on the ≥2-jet component of the merged Menlops sample directly translates into a lower bound on the jet radius parameter used to divide the Nlops and Meps samples prior to combination (the Menlops merging scale). The Meps simulation also involves a jet merging scale beneath which the distribution of radiation is determined by the parton shower approximation applied to the hard matrix element configurations generated above it. The difference in the two merging scales defines a region in phase space, in the ≥2-jet part of the sample, where the Meps simulation benefits from the use of higher order matrix elements where, in the same window of jet radii, the Menlops sample distributes jets according to a parton shower approximation applied to a hard single emission configuration. The key question concerning the quality of the approximation in Eq.4 then is: how close can one take the Menlops merging scale to that used in the Meps simulation while keeping σ(≥ 2) < αS? If the condition on the ≥ 2-jet fraction can be met and the window between the jet merging scales is small, or zero, then the exact reweighting method becomes academic with respect to the simple one in Eq.4. 4 Results: W boson production We applied the simple prescription in Eq.4 to the simulation of W boson production in 14 TeV pp collisions. We were able to merge a Powheg sample with a Meps sample with the Menlops merging scale taken down at the minimal Meps one (20 GeV in the exclusive kT clustering algorithm). The NLO and multi-jet accuracy of the results are clear in Fig. 1; for inclusive observables the Menlops and pure Nlops predictions are indistinguishable, while for exclusive jet observables they assume the form of the superior Meps simulation. References 1. S. Frixione and B. R. Webber, JHEP 0206 (2002) 029 2. P. Nason, JHEP 0411 (2004) 040 3. S. Frixione, P. Nason, and C. Oleari, JHEP 0711 (2007) 070 4. K. Hamilton, P. Nason, JHEP 1006 (2010) 039
New Results in Soft Gluon Physics C.D. WHITE School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, Scotland, UK We examine soft gluon physics, focusing on recently developed path integral methods. Two example applications of this technique are presented, namely the classification of soft gluon amplitudes beyond the eikonal approximation, and the structure of multiparton webs. The latter reveal new mathematical structures in the exponents of scattering amplitudes. 1 Introduction It is well-known that QCD radiation leads to unstable results in perturbation theory when the momentum of the emitted radiation becomes low (“soft”). Typically, if ξ is some dimensionless energy variable representing the total energy carried by soft gluons, then one finds differential cross-sections of the form dσ dξ α n,m n S = c 0 log nm m (ξ) + c ξ 1 nm log m (ξ) + ... involving large logarithms (of soft origin) to all orders in perturbation theory. Here the first set of terms can be obtained from the so-called eikonal approximation, in which the momentum of the emitted gluons formally goes to zero. Much is known already about these logarithms. The second set of terms arises from the next-to-eikonal (NE) limit, corresponding to a first order expansion in the momentum of the emitted gluons. These logarithms, although suppressed by a power of the energy scale ξ, can be numerically significant in many scattering processes. In the soft phase-space region in which ξ → 0, the above perturbation expansion breaks down in that all terms become large. The solution to this problem is to work out the logarithms to all orders in the coupling constant and sum them up (“resummation”). This is by now a highly developed subject, and many different approaches already exist for summing eikonal logarithms (e.g. Feynman diagram approaches, SCET). Here I will explain the basic idea using the web approach 1,2,3 , and using the schematic scattering process shown in figure 1. This consists of a (1)
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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
Page 152 and 153: e M(Dπ) distributions obtained D +
Page 155 and 156: CHARM PHYSICS RESULTS AND PROSPECTS
Page 157 and 158: LHCb is working towards its first m
Page 159 and 160: Two body hadronic D decays Yu Fushe
Page 161 and 162: where the effective coefficients aA
Page 163: 6. J. J. Sakurai, Phys. Rev. 156, 1
Page 166 and 167: states: 6π, 2K4π, 4K2π, KSK3π 1
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Page 170 and 171: Figure 1: The π 0 recoil mass spec
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Page 174 and 175: conservation. This second principle
Page 176 and 177: many of them come from gluon nonper
Page 179 and 180: Latest Jets Results from the Tevatr
Page 181 and 182: in for the inclusive trijet event s
Page 183 and 184: RECENT RESULTS ON JETS FROM CMS F.
Page 185 and 186: dy (pb/GeV) /dp 2 d 10 10 10 9 10
Page 187 and 188: RECENT RESULTS ON JETS WITH ATLAS G
Page 189 and 190: | y| < 0.3 ATLAS Preliminary 2.1 <
Page 191 and 192: EPOS 2 and LHC Results TanguyPierog
Page 193 and 194: positions are randomly distributed
Page 195 and 196: ABOUT THE HELIX STRUCTURE OF THE LU
Page 197 and 198: Figure 2: Left: Correlations betwee
Page 199 and 200: Improving NLO-parton shower matched
Page 201: due to the inclusion of higher orde
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
Page 217 and 218: Σ fb Σ fb 3.5 3.0 2.5 2.0 0.65 0.
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 and 248: α S (m Z 0) 0.15 0.14 0.13 0.12 0.
Page 249 and 250: Reaching beyond NLO in processes wi
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Nonlocal Condensate Model for QCD S
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The lower bound for the integration
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AN ALTERNATIVE SUBTRACTION SCHEME F
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where MBorn,g is the underlying Bor
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THE NNPDF2.1 PARTON SET F. CERUTTI
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ottom masses mb of 4.25, 4.5, 5.0 a
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HOLOGRAPHIC DESCRIPTION OF HADRONS
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∫ SYM = κ d 4 ( 1 xdzTr 2 h(z)F
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Nuclear matter and chiral phase tra
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fact that for Nc ≫ 3 a gas of fre
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Recent Results on Light Hadron Spec
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Figure 3: Mass spectrum fitting wit
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MEASUREMENT OF THE J/ψ INCLUSIVE P
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2 Counts per 40 MeV/c 120 100 80 60
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STUDY OF Ke4 DECAYS IN THE NA48/2 E
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photons were accepted while particl
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6. Structure Functions Diffraction
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2 Hadronic Final States and Diffrac
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3 Summary A brief overview of recen
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Using HERA Data to Determine the In
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k f n 0.4 0.2 0 -0.2 0.4 0.2 0 -0.2
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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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