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

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) 3 (fm long R side R out R 400 350 300 250 200 150 100 50 E895 2.7, 3.3, 3.8, 4.3 GeV NA49 8.7, 12.5, 17.3 GeV CERES 17.3 GeV STAR 62.4, 200 GeV PHOBOS 62.4, 200 GeV ALICE 2760 GeV 0 0 500 1000 1500 2000 〈 dN /dη 〉 ch (fm/c) f τ 12 10 8 6 4 2 E895 2.7, 3.3, 3.8, 4.3 GeV NA49 8.7, 12.5, 17.3 GeV CERES 17.3 GeV STAR 62.4, 200 GeV PHOBOS 62.4, 200 GeV ALICE 2760 GeV 0 0 2 4 6 8 10 12 14 〈 dN 1/3 /dη 〉 ch Figure 5: Product of the HBT radii at kT=0.3 GeV/c (left panel) and decoupling time extracted from Rlong(kT) (right panel) as a function of the mean dNch/dη. ALICE results are compared to lower energy data at the AGS, SPS and RHIC. with measurements at lower energies. It is found to be twice the value measured in the most central collisions at RHIC. The decoupling time, i.e. the time of hadron chemical freeze-out, has been measured from Rlong, which is proportional to the total duration of the longitudinal expansion. It is about 30% larger than the one measured at RHIC (Fig. 5 on the right) and a linear scaling with 1/3 is observed. The expansion of the fireball created in Pb–Pb collisions at √ s=2.76 TeV is modeled using the relativistic viscous hydrodynamics and models tuned to reproduce RHIC data still hold at the LHC and reproduce the observed growth with energy. 5 Conclusions After few weeks from the first Pb–Pb collisions, the ALICE Collaboration has extracted the main properties of the matter produced. The first measurements with Pb–Pb collisions show an increase in the multiplicity of charged particles compared to RHIC (about factor 2) but with the same centrality dependence. The increase is higher than expected. The elliptic flow is found to be stronger than at RHIC and the system created behaves as a very low viscosity fluid. As for two-pion Bose–Einstein correlations, the pion source radii and the decoupling time exceed significantly those measured at RHIC and follow the trend observed at lower energies. References 1. ALICE Collaboration K. Aamodt et al, JINST 3, S08002 (2008). 2. ALICE Collaboration K. Aamodt et al, Phys. Rev. Lett. 105, 252301 (2010). 3. ALICE Collaboration K. Aamodt et al, Phys. Rev. Lett. 106, 032301 (2011). 4. ALICE Collaboration K. Aamodt et al, Phys. Rev. Lett. 105, 252302 (2010). 5. ALICE Collaboration K. Aamodt et al, Phys. Lett. B 696, 328-337 (2011).
TWO-, THREE-, AND JET-HADRON CORRELATIONS AT STAR Kolja Kauder for the STAR Collaboration University of Illinois at Chicago, Dept. of Physics, 845 W Taylor Street M/C 273, Chicago IL 60607, USA Selected results of jet-medium interaction studies via hadron correlation techniques are presented. Jet modifications are studied using a pT -dependent autocorrelation analysis and a two-dimensional fit model, which allow connection between the observed near-side correlation structures and theory. Analysis of both sides of a di-jet-like event with the 2+1 technique provides indications of a tangential emission bias in these types of events. Jet-hadron correlations on the away-side find softening and broadening of the recoil jet in the medium. 1 Multi-Hadron Correlation Analyses The discovery of the jet-quenching effect was an early piece of evidence that a strongly-interacting medium had been created at RHIC. The nuclear modification factor (RAA) shows an inclusive yield suppression in central Au+Au collisions at 200 GeV by a factor of five compared to binary scaled pp in the fragmentation region above pT = 4 GeV/c. Such a suppression can not be seen in the cold nuclear matter created for example in d+Au collisions 1,2 . STAR’s di-hadron correlation measurement revealed a more differential insight into the mechanism of this energy loss 3 : surviving jets triggering a 4-6 GeV/c threshold appear similar or identical to those in pp or d+Au at small relative angles, whereas the away-side around ∆φ = π is severely suppressed when considering associates in the intermediate pT > 2 GeV/c range. This correlation measurement, together with RAA results, is indicative of strong energy loss in the medium that hadronic models could not successfully reproduce. To further explore the mechanisms of energy loss in the medium, a multitude of differential correlation measurements to study jets in heavy ion collisions have been developed. Here we present three selected STAR results from the past year. The main detector components relevant for this discussion are STAR’s Time Projection Chamber (TPC) for tracking of charged particles, and the Barrel Electromagnetic Calorimeter (BEMC) for triggering on high energy particles and full jet reconstruction. Both have full azimuthal coverage with nearly uniform rapidity acceptance of |η| < 1. For the results presented below, 18M central triggered and 14M minimum bias Au+Au events from year 2004 as well as 1.1M high-energy (BEMC) triggered and 74M minimum bias Au+Au events from 2007 were used. d+Au reference data comes from 5.5M events from year 2003 as well as 46M (minimum bias) and 6M (high energy) events from 2008. 150k pp high-energy events from 2006 were also used. 2 Autocorrelation The correlation of tracks in the TPC is explored by recording relative angles. Cuts on the transverse momentum of the involved particles serve to select specific kinematic regions. The
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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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Figure 2: Left: Correlations betwee
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Improving NLO-parton shower matched
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due to the inclusion of higher orde
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New Results in Soft Gluon Physics C
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Figure 2: Spacetime depiction of Dr
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Central Exclusive Meson Pair Produc
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in the CEP cross section. However i
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AN AVERAGE b-QUARK FRAGMENTATION FU
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1/N dN/dx 3.5 3 2.5 2 1.5 1 0.5 ALE
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W + W + jj at NLO in QCD: an exotic
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Σ fb Σ fb 3.5 3.0 2.5 2.0 0.65 0.
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W/Z+Jets and W/Z+HF Production at t
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Figure 2: Measured inclusive jet di
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W and Z physics with the ATLAS dete
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SHERPA 9 MC generators but not by P
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W/Z + Jets results from CMS V. CIUL
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Events / 0.1 600 500 400 300 200 10
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TEVATRON RESULTS ON MULTI-PARTON IN
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iterative midpoint cone algorithm w
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INVESTIGATIONS OF DOUBLE PARTON SCA
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¦ § ¦ ¨ ¥ ¦ ¨ § ¦ © ¦ §
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Figure 4: Two-dimensional distribut
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SOFT QCD RESULTS FROM ATLAS AND CMS
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as a function of multiplicity for t
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Determination of αS using hadronic
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α S (m Z 0) 0.15 0.14 0.13 0.12 0.
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Reaching beyond NLO in processes wi
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dσ/dp t,max [fb/GeV] 10 5 10 4 10
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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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Page 281 and 282: STUDY OF Ke4 DECAYS IN THE NA48/2 E
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Page 290 and 291: 3 Summary A brief overview of recen
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Page 297: The singular term, on the other han
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Page 303 and 304: DIFFRACTION, SATURATION AND pp CROS
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Page 311: 7. Heavy Ions
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Page 334 and 335: 3 Results 3.1 Dijet Properties in p
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Page 342 and 343: Here D is the diffusion coefficient
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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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