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Hadronic Collisions

Due to the asymptotic freedom in QCD, the interaction between quarks and gluons becomes arbitrarily weak at short distances. Consequently hadrons behave as collections of free partons at large transferred momenta and their interaction can therefore be described using a parton model. [Pg.27]


In this chapter the theoretical concepts relevant to describe the physics of heavy quarks at the LHC are introduced. The main ideas of Quantum Chromodynamics are reviewed, before their appUcation to high-energy hadron-hadron collisions is discussed. This includes the factorization ansatz, the evolution of the parton distribution functions, the partonic processes important for beauty quark production and the phenomenological treatment of heavy quark fragmentation. A further section is dedicated to the description of the decay of -hadrons via the weak interaction. The Monte Carlo event generators which are used in this analysis to generate full hadronic events within the QCD framework are presented in the last section. [Pg.25]

The leading-order (LO) process for the production of a heavy quark Q with mass mq in hadronic collisions is flavor creation, i.e. quark-antiquark annihilation and gluon-gluon fusion... [Pg.31]

M. L. Mangano, Two lectures on heavy quark production in hadronic collisions. CERN-TH/97-328 (1997)... [Pg.40]

Hadronic models deal with secondary electrons (first proposed by Dennison 1980) produced by the decay of collision/annihilation products (mainly 7r=b —> e ) of p-p (Colafrancesco Blasi 1998, Blasi Colafirancesco 1999) or x- X (e.g., Colafrancesco Mele 2001) interactions. The secondary electrons are produced in situ (thus avoiding to invoke re-acceleration) and require values 1 — 10, found to be more consistent with Faraday Rotation data. These models predict a substantial p/e ratio (like that observed in our Galaxy and in SNe remnants) and an extended modest gamma-ray emission with both hadronic and electronic signatures. The in-situ character of these models produce an extended emission both in space and in time (it is actually stationary) and a quite strong feedback on the ICM (Colafrancesco 1999, Miniafi et al. 2001). [Pg.94]

We quote here only the latest value obtained from the measured hadronic production cross section in e+e- collisions as well as the information obtained from the analysis of hadronic tau decay data [29] ... [Pg.165]

This is in good agreement with the measurements (19), (20), and (21). The uncertainty in (34) comes mainly from the hadronic vacuum-polarization contribution (30). It must be improved by at least a factor of two before we can extract useful physical information from the new high precision measurement of j. Fortunately, this contribution can be calculated from the measured value of R (= Future measurements of R at VEPP-2M, VEPP-4M, DA< NE and BEPS as well as analysis of the hadronic tau decay data [61,62,63], is expected to reduce the uncertainty of this contribution to a satisfactory level. [Pg.165]

The leptonic annihilation is nevertheless observable in hydrogen-antihydrogen collisions. Its main appearance is, however, due to indirect processes, namely the intermediate formation of positronium as a consequence of rearrangement collisions. In that case the leptons are likely to annihilate with a certain time delay after hadronic annihilation. This is because regardless the final state of positronium its life time is longer than that of the most probable final state of protonium with N = 23. [Pg.467]

Fig. 3. The cross-section for annihilation in flight in H + H collisions (in atomic units). Dashed curve leptonic annihilation in the coUisional singlet state, o- = (4.0 X 10 /y )uo- Dash-dotted curve leptonic annihilation in the coUisional triplet state, a- = (3.5 X 10 /y )ao- Solid line the total leptonic annihilation rate for spin-polarized H - - H collisions (e.g., in the magnetic trap), taken as the statistical average of the cross-sections mentioned above. The upper curve (dotted) represents the cross-section = (0.14/y/ )ao for the hadronic annihilation in flight. Fig. 3. The cross-section for annihilation in flight in H + H collisions (in atomic units). Dashed curve leptonic annihilation in the coUisional singlet state, o- = (4.0 X 10 /y )uo- Dash-dotted curve leptonic annihilation in the coUisional triplet state, a- = (3.5 X 10 /y )ao- Solid line the total leptonic annihilation rate for spin-polarized H - - H collisions (e.g., in the magnetic trap), taken as the statistical average of the cross-sections mentioned above. The upper curve (dotted) represents the cross-section = (0.14/y/ )ao for the hadronic annihilation in flight.
Fig. 4. Values of the hadronic wave function/o(k R)/R (in a.u.) at the coalescence point R = 0) for various collision energies s, = 10 (solid), 10 (dotted), 10 (dashed), 10 (longly dashed), and 10 a.u. (dot-dashed). Fig. 4. Values of the hadronic wave function/o(k R)/R (in a.u.) at the coalescence point R = 0) for various collision energies s, = 10 (solid), 10 (dotted), 10 (dashed), 10 (longly dashed), and 10 a.u. (dot-dashed).
Hadron showers (jets) from quarks and gluons produced in the decay of weak bosons as detected in high-energy electron-positron collisions by the OPAL Collaboration (OPAL 2003) at the Large Electron Positron Collider at CERN. Upper left the decay of a Z boson to a quark and an antiquark, e+e+ Z q + q (two jets). Upper right a Z boson decays to a pair of b quarks (as identified by jet properties) and one of them emits a gluon, e+e+ Z b + b + g (three jets). Below a W W pair decays to two quark-antiquark pairs (four jets). The sizes of boxes indicate the particle energies deposited in the detector elements... [Pg.467]

As mentioned before, the neutral exotic hydrogen atom (having neither Coulomb nor Pauli repulsion) can penetrate other atoms and lose its exotic particle to a heavier nucleus. As the rate of this reaction is proportional to the number of collisions, it can be detected for hadronic atoms but it is really dramatic for muonic hydrogen as its lifetime is many orders of magnitude longer in the muon-catalyzed fusion measurements, for example, the concentration of heavy impurities has to be below 10 to avoid the distortion of the results by transfer. This feature was used to study muon capture in rare gas isotopes as it is sufficient to have less than 1% krypton in hydrogen to have all muons ended up in muonic krypton states. [Pg.1500]

Soft processes resulting in the production of low momentum hadrons will be the most common events in proton-proton collision at the LHC. Although these processes are QCD related, they cannot be calculated by pQCD. Perturbative approaches only lead to reliable results if a hard scale is present in the interaction. In the case of heavy flavor physics, the hard scale is provided by the mass of the heavy quark, its transverse momentum or the virtuality of the process. [Pg.28]

It will be one of the main aims of the next chapters to discuss the phenomenology of hadron production in e e collisions in the high energy region. This, as we have already pointed out, is the natural soiurce of information on the new narrow vector meson resonances. [Pg.131]


See other pages where Hadronic Collisions is mentioned: [Pg.95]    [Pg.22]    [Pg.26]    [Pg.27]    [Pg.29]    [Pg.29]    [Pg.31]    [Pg.46]    [Pg.95]    [Pg.22]    [Pg.26]    [Pg.27]    [Pg.29]    [Pg.29]    [Pg.31]    [Pg.46]    [Pg.99]    [Pg.203]    [Pg.278]    [Pg.378]    [Pg.402]    [Pg.1212]    [Pg.411]    [Pg.10]    [Pg.276]    [Pg.327]    [Pg.244]    [Pg.203]    [Pg.467]    [Pg.467]    [Pg.919]    [Pg.210]    [Pg.369]    [Pg.466]    [Pg.629]    [Pg.1507]    [Pg.12]    [Pg.20]    [Pg.34]    [Pg.36]    [Pg.72]    [Pg.233]    [Pg.278]    [Pg.324]   


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Hadrons

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