31 research outputs found
Next-to-leading order short distance QCD corrections to the effective Hamiltonian, implications for the - mass difference
We report on the results of a calculation of next-to leading order short
distance QCD corrections to the coefficient of the effective Lagrangian in the standard model and discuss the uncertainties inherent in
such a calculation. As a phenomenological application we comment on the
contributions of short distance physics to the -- mass difference. This report is based on research work done in
collaboration with Ulrich Nierste.Comment: 4 pages and 2 figures, uses LaTeX espcrc2 documentstyle option (all
necessary files included in an uuencoded compressed tar file). Invited talk
at the conference 'QCD94', Montpellier, France, 7-13 July 1994, to appear in
the proceedings. TUM-T31-72/9
The Complete |Delta S|=2 Hamiltonian in the Next-To-Leading Order
We present the complete next-to-leading order short-distance QCD corrections
to the effective \dstwo -hamiltonian in the Standard Model. The calculation of
the coefficient is described in great detail. It involves the two-loop
mixing of bilocal structures composed of two \dsone\ operators into \dstwo\
operators. The next-to-leading order corrections enhance by 27\% to
\eta_3=0.47 \errorpm{+0.03}{-0.04} thereby affecting the phenomenology of
sizeably. depends on the physical input parameters ,
and \laMSb only weakly. The quoted error stems from renormalization
scale dependences, which have reduced compared to the old leading log result.
The known calculation of and is repeated in order to compare
the structure of the three QCD coefficients. We further discuss some field
theoretical aspects of the calculation such as the renormalization group
equation for Green's functions with two operator insertions and the
renormalization scheme dependence caused by the presence of evanescent
operators.Comment: 68 pages, requires LaTeX2e and the standard LaTeX-packages epsf.sty,
rotate.sty, a4.sty, subeqn.sty, cite.sty, array.sty, dcolumn.sty; Figures are
submitted as a seperate tar.gz-file. A complete PostScript version may be
obtained from
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-86-96.ps.gz or
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-86-96.ps2.gz
(scaled down and rotated version to print two pages on one sheet of paper).
Source available at
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-86-96.tar.g
Exclusive Radiative Decays of B Mesons
We present within the Standard Model the exclusive radiative decays B ->
K*/rho gamma and B_(s/d) -> gamma gamma in QCD factorization based on the
heavy-quark limit m_b >> Lambda_QCD. For the decays with a vector meson in the
final state we give results complete to next-to-leading order in QCD.Comment: 4 pages, contributed to QCD 02: High-Energy Physics International
Conference in Quantum Chromodynamics, Montpellier, France, 2-9 July 200
Enhancement of the -- Mass Difference by Short Distance QCD Corrections Beyond Leading Logarithms
We calculate the next-to-leading order short distance QCD corrections to the
coefficient of the effective hamiltonian in the
standard model. This part dominates the short distance contribution to the -- mass difference. The next-to-leading order
result enhances and by 20\% compared to the
leading order estimate. Taking 0.200 \gev \le \laMSb \le 0.350 \gev and 1.35
\gev \le m_c(m_c) \le 1.45 \gev we obtain compared to . For this
corresponds to 48 -- 75 \% of the experimentally observed mass difference. The
inclusion of next-to- leading order corrections to reduces
considerably the theoretical uncertainty related to the choice of
renormalization scales.Comment: 30 pages and 9 figures (available as uuencoded tarred postscript
files), LaTeX, TUM-T31-40/9
The Impact of a 4th Generation on Mixing and CP Violation in the Charm System
We study D0-D0 mixing in the presence of a fourth generation of quarks. In
particular, we calculate the size of the allowed CP violation which is found at
the observable level well beyond anything possible with CKM dynamics. We
calculate the semileptonic asymmetry a_SL and the mixing induced CP asymmetry
eta_fS_f which are correlated with each other. We also investigate the
correlation of eta_fS_f with a number of prominent observables in other mesonic
systems like epsilon'/epsilon, Br(K_L -> pi0 nu nu), Br(K+ -> pi+ nu nu),
Br(B_s ->mu+ mu-), Br(B_d -> mu+ mu-) and finally S_psi phi in the B_s system.
We identify a clear pattern of flavour and CP violation predicted by the SM4
model: While simultaneous large 4G effects in the K and D systems are possible,
accompanying large NP effects in the B_d system are disfavoured. However this
behaviour is not as pronounced as found for the LHT and RSc models. In contrast
to this, sizeable CP violating effects in the B_s system are possible unless
extreme effects in eta_fS_f are found, and Br(B_s ->mu+ mu-) can be strongly
enhanced regardless of the situation in the D system. We find that, on the
other hand, S_psi phi > 0.2 combined with the measured epsilon'/epsilon
significantly diminishes 4G effects within the D system.Comment: 22 pages, 23 figures, v2 (references added
ADAM17 substrate release in proximal tubule drives kidney fibrosis
Kidney fibrosis following kidney injury is an unresolved health problem and causes significant morbidity and mortality worldwide. In a study into its molecular mechanism, we identified essential causative features. Acute or chronic kidney injury causes sustained elevation of a disintegrin and metalloprotease 17 (ADAM17); of its cleavage-activated proligand substrates, in particular of pro-TNFα and the EGFR ligand amphiregulin (pro-AREG); and of the substrates\u27 receptors. As a consequence, EGFR is persistently activated and triggers the synthesis and release of proinflammatory and profibrotic factors, resulting in macrophage/neutrophil ingress and fibrosis. ADAM17 hypomorphic mice, specific ADAM17 inhibitor-treated WT mice, or mice with inducible KO of ADAM17 in proximal tubule (Slc34a1-Cre) were significantly protected against these effects. In vitro, in proximal tubule cells, we show that AREG has unique profibrotic actions that are potentiated by TNFα-induced AREG cleavage. In vivo, in acute kidney injury (AKI) and chronic kidney disease (CKD, fibrosis) patients, soluble AREG is indeed highly upregulated in human urine, and both ADAM17 and AREG expression show strong positive correlation with fibrosis markers in related kidney biopsies. Our results indicate that targeting of the ADAM17 pathway represents a therapeutic target for human kidney fibrosis
Indirect CP-Violation in the Neutral Kaon System Beyond Leading Logarithms
We have calculated the short distance QCD coefficient \eta_3 of the effective
|\Delta S|=2-hamiltonian in the next-to-leading order. Since now all
coefficients \eta_1, \eta_2 and \eta_3 are known beyond the leading log
approximation, one can achieve a much higher precision in the theoretical
analysis of \epsilon_K. The measured value for \epsilon_Km_t and the non-
perturbative parameter B_K as a function of the remaining three quantities. We
discuss the implications on the CKM phase \delta, |V_{td}| and the key quantity
for all CP-violating processes, Im \lambda_t = Im [V^*_{ts} V_{td}]. These
quantities and the improved Wolfenstein parameters \bar\rho and \bar\eta are
tabulated and the shape of the unitarity triangle is discussed. We compare the
range for |V_{td}| with the one obtained from the analysis of B^0--\bar{B^0}
mixing. For 0.037 \leq |V_{cb}| \leq 0.043, 0.06 \leq |V_{ub}/V_{cb}| \leq 0.10
and 0.65 \leq B_K \leq 0.85 we find from a combined analysis of \epsilon_K and
the B^0--\bar{B^0} mixing paramater x_d: 49^{\circ} \leq \delta \leq
146^{\circ}, 7.4 \cdot 10^{-3} \leq |V_{td}| \leq 12.4 \cdot 10^{-3}, 0.85
\cdot 10^{-4} \leq \imag \lambda_t \leq 1.60 \cdot 10^{-4}, -0.36 \leq \bar\rho
\leq 0.28 and 0.21 \leq \bar\eta \leq 0.44. We predict the mass difference of
the B_s^0$ system to lie in the range 6.5 ps^{-1} \leq \Delta m_{B_s} \leq 28
ps^{-1}. Finally we have a 1995 look at the K_L--K_S mass difference.Comment: 28 pages in RevTeX, uses epsf. Tables and PostScript figures
submitted seperately. A complete PostScript version may be obtained from URL
ftp://feynman.t30.physik.tu-muenchen.de/pub/preprints/tum-81-95.ps.g
Exhaled Aerosols in SARS-CoV-2 Polymerase Chain Reaction-Positive Children and Age-Matched-Negative Controls
BackgroundChildren and adolescents seem to be less affected by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease in terms of severity, especially until the increasing spread of the omicron variant in December 2021. Anatomical structures and lower number of exhaled aerosols may in part explain this phenomenon. In a cohort of healthy and SARS-CoV-2 infected children, we compared exhaled particle counts to gain further insights about the spreading of SARS-CoV-2.Materials and MethodsIn this single-center prospective observational trial, a total of 162 children and adolescents (age 6–17 years), of whom 39 were polymerase chain reaction (PCR)-positive for SARS-CoV-2 and 123 PCR-negative, were included. The 39 PCR-positive children were compared to 39 PCR-negative age-matched controls. The data of all PCR-negative children were analyzed to determine baseline exhaled particle counts in children. In addition, medical and clinical history was obtained and spirometry was measured.ResultsBaseline exhaled particle counts were low in healthy children. Exhaled particle counts were significantly increased in SARS-CoV-2 PCR-positive children (median 355.0/L; range 81–6955/L), compared to age-matched -negative children (median 157.0/L; range 1–533/L; p < 0.001).ConclusionSARS-CoV-2 PCR-positive children exhaled significantly higher levels of aerosols than healthy children. Overall children had low levels of exhaled particle counts, possibly indicating that children are not the major driver of the SARS-CoV-2 pandemic.Trial Registration[ClinicalTrials.gov], Identifier [NCT04739020]