Colour Rearrangement Research Articles

35. Atypical FISH patterns clarified by RNAseq in solid tumor specimens

Fluorescence in situ hybridization (FISH) for recurrent gene rearrangements in solid tumors can yield unexpected signal patterns, e.g. loss of one labeled portion of a dual color rearrangement probe, diminished probe signals, or duplicated/amplified probe signals. Whole transcriptome RNA sequencing (RNAseq) may help resolve gene rearrangement status.

Quantum number density asymmetries within QCD jets correlated withΛ0polarization

The observation of jets in a variety of hard-scattering processes has allowed the quantitative study of perturbative quantum chromodynamics (PQCD) by comparing detailed theoretical predictions with a wide range of experimental data. This paper examines how some important, nonperturbative, facets of QCD involving the internal dynamical structure of jets can be studied by measuring the spin orientation of Lambda particles produced in these jets. The measurement of the transverse polarization for an individual Lambda within a QCD jet permits the definition of spin-directed asymmetries in local quantum number densities in rapidity space (such as charge, strangeness and baryon number densities) involving neighboring hadrons in the jet. These asymmetries can only be generated by soft, nonperturbative dynamical mechanisms and such measurements can provide insight not otherwise accessible into the color rearrangement that occurs during the hadronization stage of the fragmentation process.

Interconnection phenomena in W pair production at DELPHI

Interactions between the products of the hadronic decays of different Ws in WW pair events can occur at several stages: from the colour rearrangement between the quarks coming from the primary branching, to the gluon exchange during the parton cascade, to the mixing of identical pions due to Bose-Einstein correlations. Besides the intrinsic interest of their study related to the understanding of the multiparticle production mechanisms, these phenomena can affect the ultimate accuracy in the W mass measurement by LEP 2. The status of the DELPHI experimental analysis on interconnection effects between W pairs hadronically decaying is reviewed in this paper.

Color evaporation induced rapidity gaps

We show that soft color rearrangement of final states can account for the appearance of rapidity gaps between jets. In the color evaporation model the probability to form a gap is simply determined by the color multiplicity of the final state. This model has no free parameters and reproduces all data obtained by the ZEUS, H1, DØ, and CDF collaborations.

Interconnection phenomena in WW events at LEP2

Interactions between the products of the hadronic decays of different Ws in WW pair events can occur at several stages: from the colour rearrangement between the quarks coming from the primary branching, to the gluon exchange during the the parton cascade, to the mixing of identical pions due to BoseEinstein correlations. Besides the intrinsic interest of their study related to the understanding of the multiparticle production mechanisms, these phenomena can affect the ultimate accuracy in the W mass measurement by LEP 2. The status of the experimental analysis on interconnection effects between W pairs decaying hadronically is reviewed in this paper. For what is related to Bose-Einstein interference, only the results from ALEPH and DELPHI are presented, being L3 and OPAL discussed in another contribution to this conference.

Color evaporation induced rapidity gaps

We show that soft color rearrangement of final states can account for the appearance of rapidity gaps between jets. In the color evaporation model the probability to form a gap is simply determined by the color multiplicity of the final state. This model has no free parameters and reproduces all data obtained by the ZEUS, H1, D\O{}, and CDF Collaborations.

Interconnections effects in multiparticle production from WW events at LEP

Interactions between the products of the hadronic decays of different Ws in WW pair events can occur at several stages: from the colour rearrangement between the quarks coming from the primary branching, to the gluon exchange during the parton cascade, to the mixing of identical pions due to Bose-Einstein correlations. Besides the intrinsic interest of their study related to the understanding of the multiparticle production mechanisms, these phenomena can affect the ultimate accuracy in the W mass measurement by LEP 2. The status of the experimental analysis on interconnection effects between W pairs hadronically decaying is reviewed in this paper.

Probability of color rearrangement at partonic level in hadronic W+W− decays

A strict method to calculate the color rearrangement probability at partonic level in hadronic W + W − decays is proposed. The color effective Hamiltonian H c is constructed from invariant amplitude for the process e +e − → W +W − → q 1 q 2q 3 q 4 + ng ( n = 0, 1, 2, …) and is used to calculate the cross sections of various color singlets and the color rearrangement probability. The true meaning of the color rearrangement is clarified and its difference from color interference is discussed.

Perturbative rates and colour rearrangement effects in four-jet events at LEP2

An important issue in the direct reconstruction method of determining the $W$ mass from $q\bar q Q\bar Q$ events at LEP2 concerns the impact of the relatively unknown QCD interconnection effects. It has been suggested that a study of `short string' states, in which colour singlet states are formed from $q \bar Q $ and $Q\bar q$ pairs with small phase--space separation, could shed important light on this issue. We show that such configurations can also be generated by conventional background $e^+e^-\ar 4$~parton processes, in particular QCD $q \bar q g g$ and $q \bar q Q \bar Q$ and non--resonant electroweak $q \bar q Q \bar Q$ production. We study the colour and kinematic structure of these background contributions, and estimate the event rate to be expected at LEP2. We find that the QCD processes are heavily suppressed, but that non--resonant $q \bar q Q \bar Q$ production may be comparable in rate to the expected `short string' signal from $W^+W^-$ production.

Transverse momentum as a measure of color topologies

Several distinct color flow topologies are possible in multiparton configurations. A method is proposed to find the correct topology, based on a minimization of the total transverse momentum of produced particles. This method is studied for three-jet ${Z}^{0}\ensuremath{\rightarrow}q\mathrm{q\ifmmode\bar\else\textasciimacron\fi{}}g$ and four-jet ${W}^{+}{W}^{\ensuremath{-}}\ensuremath{\rightarrow}{q}_{1}{\overline{q}}_{2}{q}_{3}{\overline{q}}_{4}$ events. It is shown how the basic picture is smeared, especially by parton-shower activity. The method, therefore, may not be sufficient on its own, but could still be a useful complement to others, and, e.g., help provide some handle on color rearrangement effects.

The interpretation of rapidity gaps at HERA

In leading twist deep inelastic ep scattering, the virtual photon interaction is fast compared to the time scale of soft color rearrangement. We compare the Pomeron exchange model, in which a neutral cluster is preformed, with a gluon exchange model, in which color is exchanged after the hard interaction. We find several features of the DIS data and of data on exclusive hard processes that favor a gluon exchange scenario. If correct, the postulate of soft color interactions between the produced (̄qq) system and the target has important implications for other processes. In particular, this may explain the puzzles of charmonium hadroproduction.

On colour rearrangement in hadronicW +W− evemts

We discuss the possibility of colour rearrangement in $\ee \to \W^+ \W^- \to \q_1 \qbar_2 \q_3 \qbar_4$ events, i.e.\ that the original colour singlets $\q_1 \qbar_2$ and $\q_3 \qbar_4$ may be transmuted, for instance, into new singlets $\q_1 \qbar_4$ and $\q_3 \qbar_2$. The effects on event properties could be quite large if such a rearrangement would occur instantaneously, so that gluon emission would be restricted to each of the new singlets separately. We argue that such a scenario is unlikely for two reasons. Firstly, the $\W^+$ and $\W^-$ usually decay at separate times after the $\W^+\W^-$ production, which leads to large relative phases for energetic radiation off the two constituents of a rearranged system, and a corresponding dampening of the QCD cascades. Secondly, within the perturbative scenario the colour transmutation appears only in order $\alpha_s^2$ and is colour-suppressed. Colour reconnection at longer time scales is quite feasible, however, and may affect the fragmentation phase. If so, the nature of non-perturbative QCD can be probed in a new way. We formulate several alternative toy models and use these to estimate the colour reconnection probability as a function of the event kinematics. Possible consequences for LEP~2 events are illustrated, with special attention to systematic errors in $\W$ mass determinations.