16290933
Pair-produced heavy particle topologies: MSSM neutralino properties at the LHC from gluino/squark cascade decays
Abstract.Processes of the form pp → anything → XiXj → $x\bar{x}$ + $y\bar{y}$ + notE are studied via a technique that may be viewed as an adaptation of time-honoured Dalitz plot analyses. Xi and Xj are new heavy states (with i, j =1, . . .,n), which may be identical or distinct; and $x\bar{x}$ and $y\bar{y}$ are necessarily distinct standard model (SM) fermion pairs whose invariant masses can be measured. A Dalitz-like plot of said invariant masses, $M(x\bar{x})$ versus $M(y\bar{y})$, exhibits a topology connected to the masses and specific decay chains of Xi and Xj. Aside from relatively minor details, observed patterns consist of a collection of box and wedge shapes. This collection is model-dependent: comparison of the observed pattern to the possibilities for a specific model yields information on which new particle pair combinations are actually being produced, information beyond that extractable from conventional one-dimensional invariant mass distributions. The technique is illustrated via application to the minimal supersymmetric standard model (MSSM) process pp → $ \tilde{g}\tilde{g},\tilde{g}\tilde{q},\tilde{q}\tilde{q} \to \widetilde{\chi}_i^0 \widetilde{\chi}_j^0$ → e+e- + μ+μ- notE. Here the heavy states are neutralinos $\widetilde{\chi}_i^0$ (i = 2,3,4) - note that $\widetilde{\chi}_1^0$ is excluded - which are produced in gluino/squark ($\tilde{g}$/$\tilde{q}$) cascade decay chains. Even with fairly modest expectations for the LHC performance during the first few years, this method still provides substantial insight into the neutralino mass spectrum and couplings if gluino/squark masses are relatively low (≃ 400 GeV).
40146055
Measurement of forward-backward asymmetry and Wilson coefficients in B --> K*l+l-.
We report the first measurement of the forward-backward asymmetry and the ratios of Wilson coefficients and in A9/A7 and A10/A7 in B --> K*l+l-, where l represents an electron or a muon. We find evidence for the forward-backward asymmetry with a significance of 3.4sigma. The results are obtained from a data sample containing 386 x 10(6) BB pairs that were collected on the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
100409752
Observation of B0 ---> a+-(1) (1260) pi-+
180004720
Observation of B ---> phi phi K Decays
126239408
Observation of B+ ---> K(1)(1270)+ gamma
44272712
Improved evidence for direct CP violation in B0-->pi+pi- decays and model-independent constraints on phi2.
We present a new measurement of the time-dependent CP-violating parameters in B(0)--> pi(+)pi(-) decays with 275 x 10(6) BB pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider operating at the Gamma(4S) resonance. We find 666 +/- 43 B(0) --> pi(+)pi(-) events and measure the CP-violating parameters: S(pipi) = -0.67 +/- 0.16(stat) +/- 0.06(syst) and A(pipi) = +0.56 +/- 0.12(stat) +/- 0.06(syst). We find evidence for large direct CP violation with a significance greater than 4 standard deviations for any S(pipi) value. Using isospin relations, we obtain 95.4% confidence intervals for the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle phi(2) of 0 degree < phiv(2) < 19 degrees and 71 degrees < phi(2) < 180 degrees.
14423824
Properties of color singlet chain states in e+ e- annihilation
We use the method of the color effective Hamiltonian to study the structure of color singlet chain states in ${N}_{c}=3$ and in the large ${N}_{c}$ limit. In order to obtain their total fraction when ${N}_{c}$ is finite, we illustrate how to orthogonalize these nonorthogonal states. We give numerical results for the fraction of orthogonalized states in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}\mathrm{gg}.$ With the help of a diagram technique, we derive their fraction up to ${O(1/N}_{c}^{2})$ for the general multigluon process. For large ${N}_{c}$ the singlet chain states correspond to well-defined color topologies. Therefore we may expect that the fraction of non-color-singlet-chain states is an estimate of the fraction of events where color reconnection is possible. In the case of soft gluon bremsstrahlung, we give an explicit form for the color effective Hamiltonian which leads to the dipole cascade formulation for parton showering in leading order in ${N}_{c}.$ The next-to-leading order corrections are also given for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}{g}_{1}{g}_{2}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}q\overline{q}{g}_{1}{g}_{2}{g}_{3}.$
120171906
Production percentages of excited baryons in e+e- annihilation
Two relations between the production weights for octet, decuplet (including both the ground and excited states) and singlet baryons are derived using the properties of hadronization in the stochastic quark combination scheme. From the basic relations, it is easy to understand the "spin suppression" phenomenon and the reason why singlet baryons have high multiplicities. A method for estimating the production percentages of the lowest excited baryons is given.
209845705
Color dipole chain and its hadronization in p anti-p collision
High energy pp collision is dealt with by double-string model. Each string corresponds to one initial color dipole which will radiate gluons to form color dipole chain. Such gluon radiation process is described by color dipole model. According to the quark combination rule, the total multiplicity formulae for calculating primary meson and baryon of one dipole chain are presented- The calculated yields of various final hadrons in energy range =53- 1 800GeV agree well with available data.
199685994
PROBING COLOUR SEPARATE SINGLET STATES IN E+E- ANNIHILATION AT Z0 POLE
124806737
Fragmentation of Light Initial Quarks into Charm Measons in e~+ e~- Annihilation
We study the process that the light initial quarks produced in e+ e- annihilation combine with the c from glu-on splitting to form D's (D-+D6-+D0) or D 's(D-*+ Ds*-+D*0). The 'light + heavy' bound state is described by light-cone wavefunction. The contribution of this process to D (D ) production at Z0 pole is much larger compared with that in lower energies (e.g. 10.6GeV) . For this special process, the invariant mass of D(D ) and the charm had-ron fragmented from the c quark has a unique spectrum which peaks near 2 MB if we constrain the D(D*) from all processes with energy larger than 20GeV. It is also noticeable that the produced D* in this process is dominantly longitudinally polarized, which is consistent with the OPAL data.