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

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Away-side gaussian width 1.4 1.2 1 0.8 0.6 0.4 0.2 ZYAM Normalization max. v uncertainties 2 trigger jet uncert. STAR preliminary Au+Au 0-20% HT Jet 10
Forward Physics in d+Au Collisions: Cold Nuclear Matter Probed with J/ψ Production and Pion Correlations Richard K. Seto for the PHENIX Collaboration Department of Physics and Astronomy, University of California at Riverside, Riverside, California, USA Large nuclei which provide the initial condition in high energy heavy ion collisions have turned out to be more complex and interesting than that of a simple superposition of protons and neutrons. One notable explanation of this phenomenon is the Color-Glass Condensate model of gluon saturation. The production of particles in d+Au collisions, particularly at forward rapidity, is sensitive to these effects. This talk covers two measurements made by the PHENIX collaboration: a) the production of J/ψ’s at forward rapidity, and b) the correlations of pions at forward rapidity with pions at either mid or forward rapidity. A comparison to models and their implications is discussed. 1 Introduction A major task in relativistic heavy ion physics is to explain how the strongly interacting Quark Gluon Plasma (sQGP) created at RHIC and the LHC is formed. The initial state is that of a cold nucleus which naively might be described as a superposition of nucleons, the structure of which is well known in terms of the parton distribution functions. However the production and scattering of particles behave as if the parton distribution functions in a nucleus are altered. In particular, gluons with xBJ < 0.01 appear to be suppressed. Such gluons are of particular interest, since they produce the majority of particles making up the sQGP. A variety of phenomena have been invoked to explain this modification of low-x gluons. These include shadowing, the modification of the parton distribution functions, coherence models, higher twist effects, and initial state energy loss. 9,10,11 One of the most intriguing explanation is the Color Glass Condensate (CGC),a model of gluon saturation. 5 The Heisenberg Uncertainty principle requires that the transverse size of lowx gluons in the nucleus be large. At low enough x, the gluons begin to overlap and recombine leading to a suppression. This effect is amplified in a relativistically contracted nucleus since the thickness contributes to the number of gluons which overlap in some transverse area. Scattering is no longer described by the PQCD quark-gluon diagram, but rather as the scattering of a quark with a large number of overlapping gluons i.e. a color glass condensate. This description is valid in the region of forward rapidity (low x). At backward-rapidity (moderate x) pQCD inspired calculations are more appropriate. In order to study this effect, the PHENIX experiment has measured the production of J/ψ’s and back to back π 0 pairs in d+Au collisions at √ s=200 GeV per nucleon. Of particular interest is the forward region, where sensitivity to the low-x partons is the greatest. We will compare the predictions of the CGC to a model of modified parton (primarily gluon) distribution functions in nuclei. The latest such distribution functions are due to Eskola,
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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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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 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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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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