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

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φ ∆ /d assoc dN trig 1/N 0.5 0.4 0.3 0.2 0.1 0.0 4 GeV/c < p < 6 GeV/c T,assoc 8 GeV/c < p < 15 GeV/c T,trig 0-5% ALICE preliminary Stat. uncertainties only 0 2 4 ∆φ (rad.) φ ∆ /d assoc dN trig 1/N 0.28 0.26 0.24 0.22 0.20 0.18 4 GeV/c < p < 6 GeV/c T,assoc 8 GeV/c < p < 15 GeV/c T,trig 0-5% ALICE preliminary Stat. uncertainties only 0 2 4 ∆φ (rad.) Figure 1: Per-trigger yield in an example bin: the right panel shows a zoom of the left panel. Indicated are the determined pedestal values (horizontal lines) and the v2 component (cos2∆φ term). For details see text. 2 Analysis The quantity which is obtained in this analysis is the associated per-trigger yield as function of the azimuthal angle difference: dN 1 dNassoc (∆φ) = d∆φ Ntrig d∆φ where Ntrig is the number of trigger particles to which Nassoc particles are associated at ∆φ = φtrig − φassoc. We measure this quantity for all pairs of particles where pT,assoc < pT,trig within |η| < 0.8 and normalize by ∆η = 1.6. Due to the flat acceptance in φ no mixed-event correction is needed. The per-trigger yield is extracted in bins of pT,trig and pT,assoc. Pedestal Subtraction To remove uncorrelated background from the associated yield, the pedestal value needs to be determined. This is done by fitting the region close to the minimum of the ∆φ distribution (∆φ ≈ ± π) with a constant and using this value as pedestal (zero yield 2 at minimum – ZYAM). One cannot exclude a correlated contribution in this region (e.g. from 3-jet events), and we do not claim that we only remove uncorrelated background. Instead we measure a yield with the prescription given here. To estimate the uncertainty on the pedestal determination, we use four different approaches (different fit regions as well as averaging over a number of bins with the smallest content). Fig. 1 shows the per-trigger yield for an example bin. The horizontal lines indicate the determined pedestal values; their spread gives an idea of the uncertainty. Also indicated is a background shape considering v2. The v2 values are taken from an independent measurement (a measurement of v2 at high pT similar to 5 . For the centrality class 60 − 90% no v2 measurement was available, therefore, as an upper limit, v2 is taken from the 40 − 50% centrality class as it is expected to reduce towards peripheral collisions). For a given bin the v2 background is 2〈v2,trig〉〈v2,assoc〉cos 2∆φ where the 〈...〉 is calculated taking into account the pT distribution of the trigger and associated particles. The yields are then calculated with and without removing the v2 component. Subsequently to the pedestal (and optionally v2) subtraction, the near and away side yields are integrated within ∆φ of ±0.7 and π ± 0.7, respectively. Systematic Uncertainties The influence of the following effects has been studied and considered for the systematic uncertainty on the extracted yields: detector efficiency and two-track effects, uncertainties in the centrality determination, pT resolution, the size of the integration window for the near and away-side yield as well as uncertainties in the pedestal determination. (1)
CP I 2.5 2.0 1.5 1.0 0.5 0.0 Near side 8 GeV/c destal Line: v2 subtracted ALICE preliminary p de 8 GeV/c destal Line: v2 subtracted Figure 2: ICP: the data points are calculated with a flat pedestal; the line is based on v2 subtracted yields. φ ∆ /d assoc dN trig 1/N 1.0 0.5 0.0 Data Pythia 6 GeV/c < p < 8 GeV/c T,trig 1 GeV/c < p < 4 GeV/c T,assoc ALICE preliminary pp 0.9 TeV uncorrected Stat. uncertainties only 0 2 4 ∆φ (rad.) φ ∆ /d assoc dN trig 1/N 1.5 1.0 0.5 0.0 Data Pythia 6 GeV/c destal-subtracted per-trigger yields from pp collisions at 0.9 (left) and 7TeV (right) are compared to a scaled MC (Pythia 6.4 with the tune Perugia-0). The last mentioned item has the largest contribution (7-20%) to the systematic uncertainties on ICP and IAA,Pythia. Results To quantify the effect of the in-medium energy loss, ratios of central to peripheral yields are calculated ICP = Ycentral/Yperipheral where Ycentral (Yperipheral) is the yield in central (peripheral) collisions, respectively. Fig. 2 shows ICP using the flat pedestal (data points) and v2 subtracted yields (lines). That the only significant difference is in the lowest bin of pT,assoc confirms the small influence of flow in this pT region. It should be noted that we only consider v2 here, although the v3 contribution might be of the same order, particularly for central events. The away-side suppression from in-medium energy loss is seen, as expected. Moreover, there is an unexpected enhancement above unity on the near-side. To study this further, and in particular if the enhancement is due to using peripheral events in the denominator, it is interesting to calculate IAA = YPb−Pb/Ypp where YPb−Pb (Ypp) is the yield in Pb-Pb (pp) collisions, respectively. No pp collisions at the same center-of-mass energy than the recorded Pb-Pb collisions had been produced yet at the time of this analysis. Therefore the option of using a MC as reference has been investigated. Fig. 3 compares uncorrected pedestalsubtracted per-trigger yields of pp collisions taken with ALICE to Pythia 6 6.4 with the tune Perugia-0 7 at √ s = 0.9 and 7 TeV. The MC has been scaled such that the yields on the near side agree with each other. The required scaling factor is 0.8 − 1 depending on pT. One can see
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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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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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Page 297: The singular term, on the other han
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Page 342 and 343: Here D is the diffusion coefficient
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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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