42 research outputs found
Price trend and integration of wholesale markets for onion in metro cities of India
Availability of market intelligence on various aspects like the potential markets, quantity arrived and prevailing and expected prices in different regions during different months of the year are important in mitigating many of market related problems. Study reveals that there was high variability in the arrival of onion in the month of March and April in selected markets. Among the markets, the coefficient of variation in both arrivals and prices were found to be higher in Ahmedabad and Kolkata. The zero order correlation matrix between two markets average wholesale prices of onion indicated the high integration among the selected markets except Ahmedabad with Mumbai market. This might be due to the movement of produce from one market area to another depending upon price prevailed in the markets. The competitive conditions prevailing in the selected markets might have influenced the movement of prices in the same direction. The magnitude of regression coefficient revealed that an increase in market arrivals by a MT in a month led to an increase in prices by Rs.6.00/MT and Rs. 0.40/MT in Bangalore and Delhi markets respectively. On the contrary, prices of onion decreased in Ahmedabad (Rs. 6.00), Mumbai (Rs. 10.00) and Kolkata (Rs. 2.00) markets with increase in arrivals by one MT in a month. Key words: Instability, Market integration, Price behavio
Resumming the color-octet contribution to e+ e- -> J/psi + X
Recent observations of the spectrum of J/psi produced in e+ e- collisions at
the Upsilon(4S) resonance are in conflict with fixed-order calculations using
the Non-Relativistic QCD (NRQCD) effective field theory. One problem is that
leading order color-octet mechanisms predict an enhancement of the cross
section for J/psi with maximal energy that is not observed in the data.
However, in this region of phase space large perturbative corrections (Sudakov
logarithms) as well as enhanced nonperturbative effects are important. In this
paper we use the newly developed Soft-Collinear Effective Theory (SCET) to
systematically include these effects. We find that these corrections
significantly broaden the color-octet contribution to the J/psi spectrum. Our
calculation employs a one-stage renormalization group evolution rather than the
two-stage evolution used in previous SCET calculations. We give a simple
argument for why the two methods yield identical results to lowest order in the
SCET power counting.Comment: 27 pages, 7 figure
Hard Scattering Factorization from Effective Field Theory
In this paper we show how gauge symmetries in an effective theory can be used
to simplify proofs of factorization formulae in highly energetic hadronic
processes. We use the soft-collinear effective theory, generalized to deal with
back-to-back jets of collinear particles. Our proofs do not depend on the
choice of a particular gauge, and the formalism is applicable to both exclusive
and inclusive factorization. As examples we treat the pi-gamma form factor
(gamma gamma* -> pi^0), light meson form factors (gamma* M -> M), as well as
deep inelastic scattering (e- p -> e- X), Drell-Yan (p pbar -> X l+ l-), and
deeply virtual Compton scattering (gamma* p -> gamma(*) p).Comment: 35 pages, 4 figures, typos corrected, journal versio
On Power Suppressed Operators and Gauge Invariance in SCET
The form of collinear gauge invariance for power suppressed operators in the
soft-collinear effective theory is discussed. Using a field redefinition we
show that it is possible to make any power suppressed ultrasoft-collinear
operators invariant under the original leading order gauge transformations. Our
manipulations avoid gauge fixing. The Lagrangians to O(lambda^2) are given in
terms of these new fields. We then give a simple procedure for constructing
power suppressed soft-collinear operators in SCET_II by using an intermediate
theory SCET_I.Comment: 15 pages, journal versio
Reducing theoretical uncertainties in mb and lambda1
We calculate general moments of the lepton energy spectrum in inclusive
semileptonic B -> X_c l \nu decay. Moments which allow the determination of
mb^{1S} and lambda1 with theoretical uncertainties Delta(mb^{1S}) ~ 0.04 GeV
and Delta(lambda1) ~ 0.05 GeV^2 are presented. The short distance 1S mass is
used to extract a mass parameter free of renormalon ambiguities. Moments which
are insensitive to mb and lambda1 and therefore test the size of the 1/mb^3
matrix elements and the validity of the OPE are also presented. Finally, we
give an expression for the total branching ratio with a lower cut on the lepton
energy, which allows one to eliminate a source of model dependence in current
determinations of |Vcb| from B -> X_c l \nu decay.Comment: 8 pages, one figur
Strong Phases and Factorization for Color Suppressed Decays
We prove a factorization theorem in QCD for the color suppressed decays B0->
D0 M0 and B0-> D*0 M0 where M is a light meson. Both the color-suppressed and
W-exchange/annihilation amplitudes contribute at lowest order in LambdaQCD/Q
where Q={mb, mc, Epi}, so no power suppression of annihilation contributions is
found. A new mechanism is given for generating non-perturbative strong phases
in the factorization framework. Model independent predictions that follow from
our results include the equality of the B0 -> D0 M0 and B0 -> D*0 M0 rates, and
equality of non-perturbative strong phases between isospin amplitudes,
delta(DM) = delta(D*M). Relations between amplitudes and phases for M=pi,rho
are also derived. These results do not follow from large Nc factorization with
heavy quark symmetry.Comment: 38 pages, 6 figs, typos correcte
A connection between inclusive semileptonic decays of bound and free heavy quarks
A relativistic constituent quark model, formulated on the light-front, is
used to derive a new parton approximation for the inclusive semileptonic decay
width of the B-meson. A simple connection between the decay rate of a free
heavy-quark and the one of a heavy-quark bound in a meson or in a baryon is
established. The main features of the new approach are the treatment of the
b-quark as an on-mass-shell particle and the inclusion of the effects arising
from the b-quark transverse motion in the B-meson. In a way conceptually
similar to the deep-inelastic scattering case, the B-meson inclusive width is
expressed as the integral of the free b-quark partial width multiplied by a
bound-state factor related to the b-quark distribution function in the B-meson.
The non-perturbative meson structure is described through various quark-model
wave functions, constructed via the Hamiltonian light-front formalism using as
input both relativized and non-relativistic potential models. A link between
spectroscopic quark models and the B-meson decay physics is obtained in this
way. Our predictions for the B -> X_c l nu_l and B -> X_u l nu_l decays are
used to extract the CKM parameters |V_cb| and |V_ub| from available inclusive
data. After averaging over the various quark models adopted and including
leading-order perturbative QCD corrections, we obtain |V_cb| = (43.0 +/-
0.7_exp +/- 1.8_th) 10^-3 and |V_ub| = (3.83 +/- 0.48_exp +/- 0.14_th) 10^-3,
implying |V_ub / V_cb| = 0.089 +/- 0.011_exp +/- 0.005_th, in nice agreement
with existing predictions.Comment: revised version with pQCD corrections included, to appear in Physical
Review
Semileptonic B_c-meson decays in sum rules of QCD and NRQCD
The semileptonic B_c-meson decays into the heavy quarkonia J/\psi (\eta_c)
and a pair of leptons are investigated in the framework of three-point sum
rules of QCD and NRQCD. Calculations of analytical expressions for the spectral
densities of QCD and NRQCD correlators with account for the Coulomb-like
\alpha_s/v terms are presented. The generalized relations due to the spin
symmetry of NRQCD for the form factors of B_c\to J/\psi (\eta_c)l\nu_l
transitions with l denoting one of the leptons e, \mu or \tau, are derived at
the recoil momentum close to zero. This allows one to express all NRQCD form
factors through a single universal quantity, an analogue of Isgur-Wise function
at the maximal invariant mass of lepton pair. The gluon condensate corrections
to three-point functions are calculated both in full QCD in the Borel transform
scheme and in NRQCD in the moment scheme. This enlarges the parameteric
stability region of sum rule method, that makes the results of the approach to
be more reliable. Numerical estimates of widths for the transitions of B_c\to
J/\psi (\eta_c)l\nu_l are presented.Comment: 37 pages, Latex file, 10 figures, 15 epsf-insertions, revised version
to appear in Nucl.Phys.
Power counting and effective field theory for charmonium
We hypothesize that the correct power counting for charmonia is in the
parameter Lambda_QCD/m_c, but is not based purely on dimensional analysis (as
is HQET). This power counting leads to predictions which differ from those
resulting from the usual velocity power counting rules of NRQCD. In particular,
we show that while Lambda_QCD/m_c power counting preserves the empirically
verified predictions of spin symmetry in decays, it also leads to new
predictions which include: A hierarchy between spin singlet and triplet octet
matrix elements in the J/psi system. A quenching of the net polarization in
production at large transverse momentum. No end point enhancement in radiative
decays. We discuss explicit tests which can differentiate between the
traditional and new theories of NRQCD.Comment: 18 pages, 1 figure Replaced plot of the psi polarization parameter
alpha as a function of transverse momentum. Alpha is now closer to zero for
large transverse moment
Gluino Contribution to Radiative B Decays: Organization of QCD Corrections and Leading Order Results
The gluino-induced contributions to the decay b-> s gamma are investigated in
supersymmetric frameworks with generic sources of flavour violation. It is
shown that, when QCD corrections are taken into account, the relevant operator
basis of the Standard Model effective Hamiltonian gets enlarged to contain: i)
magnetic and chromomagnetic operators with a factor of alpha_s and weighted by
a quark mass m_b or m_c; ii) magnetic and chromomagnetic operators of lower
dimensionality, also containing alpha_s; iii) four-quark operators weighted by
a factor alpha_s^2. Numerical results are given, showing the effects of the
leading order QCD corrections on the inclusive branching ratio for b-> s gamma.
Constraints on supersymmetric sources of flavour violation are derived.Comment: 36 pages including 16 postscript figures; uses epsf; journal version:
one ref. added; rephrasing of a couple of paragraph