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

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process, gain better insight into the significance of σeff. A firm basis is desirable for Eq. (1) starting from the formal expression for the differential cross section in terms of the absolute square of the full matrix element integrated over phase space: dσ(pp → b¯bj1j2X) = 1 2s |M(pp → b¯bj1j2X)| 2 dPSb¯bj1j2X . (4) The amplitude M(pp → b ¯ bj1j2X) should include a sum of amplitudes for 2-parton collisions (one active from each incident hadron, i.e., 2 → 4); 3-parton collisions (two active from one hadron and one active from the other); and 4-parton collisions (two active from each hadron or three from one and one from the other), and so forth that all yield the same 4 parton final state. There will be contributions to the final state from the squares of individual amplitudes as well as interference terms. Specializing to 4 → 4, the DPS case, one would start from a 4-parton → 4-parton hard part. Not evident at this time is how the four-parton matrix element can be reduced to a product of two matrix elements for the single parton scatterings, needed for Eq. (1). The demonstration of clear DPS signals in LHC data would be an important stimulus for further theoretical studies. Acknowledgments This work was done in collaboration with Chris Jackson and Gabe Shaughnessy and supported financially by the U. S. Department of Energy under Contract No. DE-AC02-06CH11357. I acknowledge valuable discussions with Tom LeCompte and Jianwei Qiu. References 1. E. L. Berger, C. B. Jackson and G. Shaughnessy, Phys. Rev. D 81, 014014 (2010) [arXiv:0911.5348 [hep-ph]] and numerous references therein. 2. V. M. Abazov et al. [D0 Collaboration], Phys. Rev. D 81, 052012 (2010) [arXiv:0912.5104 [hep-ex]] and earlier experimental references cited therein. 3. J. R. Gaunt and W. J. Stirling, JHEP 1003 (2010) 005 [arXiv:0910.4347 [hep-ph]].
SOFT QCD RESULTS FROM ATLAS AND CMS CLAUDIA-ELISABETH WULZ, for the ATLAS and CMS Collaborations Institute of High Energy Physics of the Austrian Academy of Sciences, Nikolsdorfergasse 18, 1050 Vienna, Austria The ATLAS and CMS Collaborations have measured properties of minimum bias events and have determined characteristics of the underlying event in proton-proton collisions at three LHC centre-of-mass energies. Comparisons to common phenomenological models and partially to other experiments have been made. The production of the strange particles K 0 S, Λ and Ξ is discussed. Particle correlation studies, in particular Bose-Einstein as well as long- and short-range angular correlations in proton-proton and lead ion events are explained. 1 Properties of minimum bias events Ideally minimum bias events are those recorded with a totally inclusive trigger. The exact definition depends on the experiment. Usually minimum bias only refers to non-single-diffractive (NSD) events. In ATLAS 1 and CMS 2 similar minimum bias trigger detectors are used. AT- LAS has two stations of Minimum Bias Trigger Scintillators (MBTS) located upstream and downstream at z = ±3.56 m from the nominal collision vertex in the pseudorapidity intervals 2.09 < |η| < 2.82 and 2.82 < |η| < 3.84. CMS has Beam Scintillator Counters (BSC) at z = ±10.86 m within 3.23 < |η| < 4.65. Both experiments also use signals from a beam pick-up based timing system (BPTX) at z = ±175 m with a time resolution of 200 ps in their minimum bias trigger. Transverse momentum spectra of charged particles have been measured in a large range of pT . Fig. 1 shows results from the CMS experiment and comparisons to CDF data 3 . Calorimeterbased transverse energy triggers have been used in the high-pT -region instead of the normal minimum bias trigger. The data are fully corrected. The inclusive invariant cross-section expressed as a function of the scaling variable xT = 2pT / √ s is given by Eq. 1. E d3σ dp3 = F (xT )/p n(xT , √ s) T = F ′ (xT )/ √ s n(xT , √ s) Minimum bias pseudorapidity and multiplicity distributions as measured by ATLAS 4 are depicted in Fig. 2. The rapidity plateau extends to |η| ≈ 1 for both centre-of-mass energies of 0.9 and 7 TeV, however, there is an increase of almost a factor of two in its height. No Monte Carlo tune describes the multiplicity distribution shown in Fig. 2c well. 2 Underlying event studies The underlying event (UE) comprises all particles except those from a given hard interaction of interest. It has components from multiple semi-hard parton scattering processes and soft (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
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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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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
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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
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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
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Page 227 and 228: W/Z + Jets results from CMS V. CIUL
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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: Figure 4: Two-dimensional distribut
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Page 245 and 246: Determination of αS using hadronic
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Page 249 and 250: Reaching beyond NLO in processes wi
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Page 253 and 254: Nonlocal Condensate Model for QCD S
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Page 265 and 266: HOLOGRAPHIC DESCRIPTION OF HADRONS
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Page 281 and 282: STUDY OF Ke4 DECAYS IN THE NA48/2 E
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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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