Searcharxiv⌕ Search

arXiv subjects

Jure Zupan

Publications and source records attributed to Jure Zupan.

At least 145 records · Page 8Linked to original sources
arXiv2008

Smoking Guns for On-Shell New Physics at the LHC

Using Tevatron bounds we derive upper limits on the LHC Higgs production rate under the assumption that no beyond the Standard Model (BSM) particles are being produced near their mass shell. A violation of these limits would constitute a smoking gun for light BSM particles. Furthermore, we demonstrate how R_T, the ratio of the partially integrated Higgs transverse momentum distribution to the inclusive rate, can also be used as a probe of light BSM particles. This ratio is insensitive to heavy virtual effects and can be well-approximated by its SM value, i.e. it is model independent. The perturbative expansion for R_T has reduced renormalization scale dependence, at the order of 5% at next-to-leading order in QCD, due to a cancellation of Wilson coefficients. A deviation from the SM value implies that light BSM particles are being produced near their mass shell. We discuss a possible loophole to this conclusion, namely the existence of a non-perturbative, CP violating sector that couples to the Higgs. We use a toy model with colored scalars to demonstrate how the model independent prediction for R_T is approached as the mass of the scalar becomes large.

hep-ph↗
arXiv2008

Constraint on rho-bar, eta-bar from B to K*pi

A linear CKM relation, $\barη= \tanΦ_{3/2}(\barρ-0.24\pm 0.03)$, involving a $1σ$ range for $Φ_{3/2}$, $20^\circ < Φ_{3/2} < 115^\circ$, is obtained from $B^0\to K^*π$ amplitudes measured recently in Dalitz plot analyses of $B^0\to K^+π^-π^0$ and $B^0(t)\to K_Sπ^+π^-$. This relation is consistent within the large error on $Φ_{3/2}$ with other CKM constraints which are unaffected by new $b\to s\bar q q$ operators. Sensitivity of the method to a new physics contribution in the $ΔS=ΔI=1$ amplitude is discussed.

hep-ph↗
arXiv2008

New Physics at a Super Flavor Factory

The potential of a Super Flavor Factory (SFF) for searches of New Physics is reviewed. While very high luminosity B physics is assumed to be at the core of the program, its scope for extensive charm and tau studies are also emphasized. The possibility to run at the Upsilon(5S) is also very briefly discussed; in principle, this could provide very clean measurements of B_s decays. The strength and reach of a SFF is most notably due to the possibility of examining an impressive array of very clean observables. The angles and the sides of the unitarity triangle can be determined with unprecedented accuracy. These serve as a reference for New Physics (NP) sensitive decays such as B^+ ->tau^+ nu and penguin dominated hadronic decay modes, providing tests of generic NP scenarios with an accuracy of a few percent. Besides, very precise studies of direct and time dependent CP asymmetries in radiative B decays and forward-backward asymmetry studies in B-> X_s l^+ l^- and numerous null tests using B, charm and tau decays are also likely to provide powerful insights into NP. The dramatic increase in luminosity at a SFF will also open up entirely new avenues for probing NP observables, e.g. by allowing sensitive studies using theoretically clean processes such as B -> X_s nu nubar. The SFF is envisioned to be a crucial tool for essential studies of flavor in the LHC era, and will extend the reach of the LHC in many important ways.

hep-ph↗
arXiv2007

Probing Minimal Flavor Violation at the LHC

If the LHC experiments discover new particles that couple to the Standard Model fermions, then measurements by ATLAS and CMS can contribute to our understanding of the flavor puzzles. We demonstrate this statement by investigating a scenario where extra SU(2)-singlet down-type quarks are within the LHC reach. By measuring masses, production cross sections and relative decay rates, minimal flavor violation (MFV) can in principle be excluded. Conversely, these measurements can probe the way in which MFV applies to the new degrees of freedom. Many of our conclusions are valid in a much more general context than this specific extension of the Standard Model.

hep-ph↗
arXiv2007

Predictions for sin 2(beta/phi_1)_eff in b->s penguin dominated modes

We provide a review of predictions for sin 2beta_eff in b->s penguin dominated modes based on 1/m_b expansion and/or SU(3) flavor symmetry. The experimental results are consistently lower than the theoretical predictions. In order to interpret whether this effect is a sign of new physics contributions or can be explained away within the Standard Model a theoretical input cannot be avoided. The effect survives at a level larger than 2.1 sigma in a conservative average over different modes that includes theoretical predictions.

hep-ph↗
arXiv2007

Probing electroweak physics using B -> XM decays in the endpoint region

Using soft-collinear effective theory we describe at leading order in 1/m_b all the semi-inclusive hadronic B -> XM decays near the endpoint, where an energetic light meson M recoils against an inclusive jet X. We also include the decays involving eta, eta' mesons that receive additional contributions from gluonic operators. The predicted branching ratios and CP asymmetries depend on fewer hadronic parameters than the corresponding two-body B decays. This makes semi-inclusive hadronic B -> XM decays a powerful probe of the potential nonperturbative nature of charming penguins as well as a useful probe of new physics effects in electroweak flavor changing transitions. A comparison with B -> KX data from BaBar points to an enhanced charming penguin, albeit with large experimental errors.

hep-ph↗
arXiv2007

Enhanced effects on extracting γfrom untagged B^0 and B_s decays

The weak phase γcan be determined using untagged B^0\to DK_S or B_s\to Dϕ, Dη^{(')} decays. In the past, the small lifetime difference y\equiv ΔΓ/(2Γ) has been neglected in B^0, while the CP violating parameter ε\equiv 1-|q/p|^2 has been neglected in both B^0-\bar B^0 and B_s-\bar B_s mixing. We estimate the effect of neglecting y and ε. We find that in D decays to flavor states this introduces a systematic error, which is enhanced by a large ratio of Cabibbo-allowed to doubly Cabibbo-suppressed D decay amplitudes.

hep-ph↗
arXiv2006

Improved method for CKM constraints in charmless three-body B and B_s decays

Recently Ciuchini, Pierini and Silvestrini proposed a method for constraining CKM parameters in B->K pi pi and B_s-> K pi pi through phase measurements of amplitudes involving I=3/2 K*pi final states. We show that complementary information on CKM parameters may be obtained by studying the phases of Delta I=1 B->(K*pi)_{I=1/2}, B_s->(K*\bar K)_{I=1} and B_s->(\bar K* K)_{I=1} amplitudes. Hadronic uncertainties in these constraints from electroweak penguin operators O_9 and O_10, studied using flavor SU(3), are shown to be very small in B->K pi pi and B_s->K pi pi and somewhat larger in B_s-> K\bar K pi. The first processes imply a precise linear relation between \bar rho and \bar eta, with a measurable slope and an intercept at \bar eta=0 involving a theoretical error of 0.03. The decays B_s-> K pi pi permit a measurement of gamma involving a theoretical error below a degree. We note that while time-dependence is required when studying B^0 decays at the Upsilon(4S), it may not be needed when studying B_s decays at hadronic colliders.

hep-ph↗
arXiv2006

Updated bounds on CP asymmetries in $B^0 \to η' K_S$ and $B^0 \to π^0 K_S$

New rate measurements of $B^0$ decays into $π^0π^0, π^0η, π^0η', ηη, ηη', η'η'$ and $K^+ K^-$ are used in conjunction with flavor SU(3) to constrain the coefficients $S$ and $C$ of $\sinΔmt$ and $\cosΔmt$ in the time-dependent CP asymmetries of $B^0 \to η' K_S$ and $B^0 \to π^0 K_S$. Experimental values of $S_{η' K}$ are now seen to be closer to the Standard Model expectations, fully consistent with the new improved bounds.

hep-ph↗
arXiv2006

Two body B decays with isosinglet final states in SCET

Expressions for decay amplitudes of B0, B- and Bs mesons to two light pseudoscalar or vector mesons, including isosinglet mesons eta, eta', omega, phi, are obtained using Soft Collinear Effective Theory at LO in 1/mb. These are then used to predict unmeasured branching ratios, direct and indirect CP asymmetries in B0, B- and Bs decays into two light pseudoscalars, following a determination of nonperturbative SCET parameters from existing data using a chi-squared fit. A separate discussion of indirect CP asymmetries in penguin dominated B0 --> eta' K(S/L), pi0 K(S/L) decays is given.

hep-ph↗
arXiv2006

Semi-inclusive hadronic B decays in the endpoint region

We consider in the soft-collinear effective theory semi-inclusive hadronic B decays, B-> XM, in which an energetic light meson M near the endpoint recoils against an inclusive jet X. We focus on a subset of decays where the spectator quark from the B meson ends up in the jet. The branching ratios and direct CP asymmetries are computed to next-to-leading order accuracy in alpha_s and to leading order in 1/m_b. The contribution of charming penguins is extensively discussed, and a method to extract it in semi-inclusive decays is suggested. Subleading 1/m_b corrections and SU(3) breaking effects are discussed.

hep-ph↗
arXiv2005

The Effect of $D-\bar D$ Mixing on the Measurement of $γ$ in $B\to D K$ Decays

$D-\bar D$ mixing is the source of the largest theoretical uncertainty in the extraction of $γ$ from $B\to D K$ decays. In the Standard Model, the mixing can have a rate close to its current experimental upper bound and is CP-conserving to an excellent approximation. We show that neglecting CP-conserving $D-\bar D$ mixing leads to an error in the determination of $γ$ only at second order in the small parameters, $Δm_D/Γ_D$ and $ΔΓ_D/Γ_D$, and is therefore very small and can be safely neglected.

hep-ph↗
arXiv2004

Determining alpha and gamma - theory

In this short review presented at FPCP04, Daegu, Korea, we discuss methods leading to determinations of alpha and gamma with practically no theoretical error. The remaining theoretical errors due to isospin breaking, neglecting of electroweak penguins or coming from other sources are addressed.

hep-ph↗
arXiv2004

The hidden strangeness mechanism in Ds^+ -> omega pi^+ and Ds^+ -> rho^0 pi^+ decays

We study possible contributions to the Ds^+ -> omega pi^+ and Ds^+ -> rho^0 pi^+ decay amplitudes. The Ds^+ -> omega pi^+ decay amplitude vanishes when the naive factorization is used, while the Ds^+ -> rho^0 pi^+ decay amplitude arises due to the annihilation contribution. We find that amplitudes for both decays might be a result of the internal K, K^* exchange. The Ds^+ -> omega pi^+ amplitude might obtain additional contribution from Ds^+ -> rho^0 eta (eta') re-scattering. The low experimental bound on the Ds^+ -> rho^0 pi^+ rate can be understood as a result of combination of the pi(1300) pole dominated annihilation contribution and the K,K^* internal exchanges. The calculated branching fractions for Ds^+ -> omega pi^+ and Ds^+ -> rho^0 pi^+ are in agreement with the current experimental results.

hep-ph↗
arXiv2004

Correlated bounds on CP asymmetries in $B^0 \to η' K_S$

Flavor SU(3) is used to constrain the coefficients of $\sinΔmt$ and $\cosΔmt$ in the time-dependent CP asymmetry of $B^0 \to η' K_S$. Correlated bounds in the $(S_{η' K}, C_{η' K})$ plane are derived, by using recent rate measurements of $B^0$ decays into $K^+ K^-, π^0π^0, π^0η, π^0η', ηη, ηη', η'η'$. Stringent bounds are obtained when assuming a single SU(3) singlet amplitude and when neglecting annihilation-type amplitudes.

hep-ph↗
arXiv2003

Chiral corrections and lattice QCD results for fBs/fBd and (Delta ms/Delta md)

It has been argued recently that the inclusion of the chiral logarithms in extrapolation of the lattice data can shift the value of the hadronic parameter xi = (fBs sqrt(B_{Bs}))/(fBd sqrt(B_{Bd})), from 1.16(6) to 1.32(10) and even higher. If true, that would considerably change the theoretical estimate for the ratio of oscillation frequencies in the neutral Bs- and Bd-systems, and would affect the standard CKM unitarity triangle analysis. In this letter we show that (fBs/fBd) \approx (fK/fpi), and thus the uncertainty due to the missing chiral logs is smaller than previously thought. By combining the NLO chiral expansion with the static heavy quark limit we obtain xi = 1.22(8).

hep-ph↗
arXiv2003

B --> pi and B --> K transitions in partially quenched chiral perturbation theory

We study the properties of the B-->pi and B-->K transition form factors in partially quenched QCD by using the approach of partially quenched chiral perturbation theory combined with the static heavy quark limit. We show that the form factors change almost linearly when varying the value of the sea quark mass, whereas the dependence on the valence quark mass contains both the standard and chirally divergent (quenched) logarithms. A simple strategy for the chiral extrapolations in the lattice studies with Nsea=2 is suggested. It consists of the linear extrapolations from the realistically accessible quark masses, first in the sea and then in the valence quark mass. From the present approach, we estimate the uncertainty induced by such extrapolations to be within 5%.

hep-lat↗