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

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and Aridane is generated. Pythia is used as the default choice and the other event generators are used to estimate the systematic uncertainty. The validity of the Monte Carlo models is tested with a comparison between the theoretical NNLO calculations and the Monte Carlo predictions at parton level. The difference between the NNLO prediction and the Monte Carlo model is well covered by using the different Monte Carlo as systematic uncertainty. For the analysis well measured hadronic events are selected. For data taken above the Z 0 - resonance events with large initial state radiation are removed. Above the W-pair threshold the expected contribution from this four-fermion processes are removed. 2 Results 2.1 Fit procedure To measure the strong coupling αS event shape observables are built from selected hadronic events together with using the theoretical predictions. These observables are constructed in a way that they show a large sensitivity to the strong coupling αS. The theoretical prediction is then fitted to the data distribution with αS being the only free parameter. The following event shape observables are used: Thrust, heavy jet mass, the total and the wide jet broadening, the C-parameter and the two-three transition parameter using the Durham jet algorithm. The fit range is determined by requiring the corrections to be small as well as the theoretical predictions to be stable within the fit range. To compare this analysis with the previous analysis the data is also fitted to next-to-leading (NLO) and NLO combined with resummed NLLA calculations. The result from the previous analysis can be reproduced. To asses the systematic uncertainty the fit is repeated in slightly different ways. Besides the uncertainty due to the correction for hadronization effects, as described in 1.1, uncertainties due to the experimental technique and uncertainties due to the incomplete power series of the theoretical prediction are evaluated. The overall uncertainty is completed by the statistical uncertainty originating from the finite statistics used in the analysis. The main motivation for the re-analysis of the data is the availability of improved theoretical calculations. In the past this uncertainty related to the theoretical prediction dominated the overall uncertainty. However, even with the new improved theoretical predictions the overall uncertainty is still dominated by the theoretical uncertainty. The statistical uncertainty, the experimental uncertainty and the hadronization uncertainty are similar, while the theoretical uncertainty is at least twice as large. 2.2 Combination of results A single value of the strong coupling αS is measured for each event shape observable and for each energy interval separately. In order to obtain a single value for each event shape observable or at each energy interval the values of αS are combined. The correlation between the different event shape observables and the different energy intervals are taken into account. The combined result for each event shape observable is shown in Fig. 1. It can be clearly seen that the scatter of the αS-values obtained with different event shape observables using NNLO predictions is smaller compared to the measurement using NLO predictions only. In addition it can be observed, that the overall uncertainty is reduced with including higher order predictions in the measurement. The increase of the uncertainty between NNLO and matched NNLO+NLLA calculations can be explained by the fact that the NNLO renormalization scale variation is compensated in two loops, while the NLLA renormalization scale variation compensation is only in one loop. The final result combining all event shape observables at all energy intervals is αS(M Z 0) = 0.1201±0.0008(stat.)±0.0013(exp.)±0.0010(had.)±0.0024(theo.) using NNLO calculations
α S (m Z 0) 0.15 0.14 0.13 0.12 0.11 0.1 NLO 1-T MH BT BW C D y23 NLO +NLLA 1-T MH BT BW C D y23 NNLO 1-T MH BT BW C D y23 NNLO +NLLA 1-T MH BT BW C D y23 Figure 1: The measured value of αS for the different event shape observables combined over the complete centerof-mass energy range. The inner uncertainty bar corresponds to the statistical uncertainty the outer one to the total uncertainty. The yellow band represents the combined αS-value an its uncertainty for all event shape observables using NLO, NLO+NLLA, NNLO and NNLO+NLLA calculations. only and αS(M Z 0) = 0.1189± 0.0008(stat.)±0.0016(exp.)±0.0010(had.)±0.0036(theo.) using combined NNLO+NLLA predictions. 2.3 Renormalization scale dependence and running of αS The dependence of the result on the choice of the renormalization scale is studied. The fixedorder predictions return for the fit the smallest χ 2 -values at a very small renormalization scales, while using the matched NNLO+NLLA predictions smaller χ 2 -values for larger renormalization scales are returned. Together with the re-analyzed JADE result 4 this analysis confirms the running of the strong coupling αS with center-of-mass energy, as predicted by QCD. 3 Summary The availability of NNLO predictions for the annihilation of an electron-positron-pair into a pair of quarks lead to a re-analysis of data taken with the OPAL detector. The combined value obtained for the strong coupling using NNLO+NLLA calculations results to αS(M Z 0) = 0.1189±0.0008(stat.)±0.0016(exp.)±0.0010(had.)±0.0036(theo.), with the overall uncertainty being dominated by missing higher order terms in the theoretical prediction. The result is consistent with the world average 8 . The result obtained can be compared to similar analyses using NNLO- and NNLO-calculations matched with NLLA 4 5 6 7 . A summary of these results is shown in Fig. 2. As seen in this analysis the results obtained using NNLO+NLLA predictions lead to smaller αS-value compared to a pure NNLO fit. The smallest overall uncertainty is obtained with a fit to the three-jet rate. Several ways to measure the strong coupling αS using
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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
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 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: Determination of αS using hadronic
Page 249 and 250: Reaching beyond NLO in processes wi
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Page 253 and 254: Nonlocal Condensate Model for QCD S
Page 255 and 256: The lower bound for the integration
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
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Page 265 and 266: HOLOGRAPHIC DESCRIPTION OF HADRONS
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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
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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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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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