Publications (884)1211.01 Total impact
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ABSTRACT: The production of $\chi_b$ mesons in protonproton collisions is studied using a data sample collected by the LHCb detector, at centreofmass energies of $\sqrt{s}=7$ and $8$~TeV and corresponding to an integrated luminosity of 3.0~fb$^{1}$. The $\chi_b$ mesons are identified through their decays to $\Upsilon(1S)\gamma$ and $\Upsilon(2S)\gamma$ using photons that converted to $e^+e^$ pairs in the detector. The $\chi_b(3P)$ meson mass, and the relative prompt production rate of $\chi_{b1}(1P)$ and $\chi_{b2}(1P)$ mesons as a function of the $\Upsilon(1S)$ transverse momentum in the $\chi_b$ rapidity range $2.0<y<4.5$, are measured. Assuming a mass splitting between the $\chi_{b1}(3P)$ and the $\chi_{b2}(3P)$ states of 10.5 MeV/$c^2$, the mass of the $\chi_{b1}(3P)$ meson is \begin{equation*} m(\chi_{b1}(3P))= 10515.7^{+2.2}_{3.9}(stat) ^{+1.5}_{2.1}(syst) MeV/c^2. \end{equation*} 
Article: Measurements of $C\!P$ violation in the threebody phase space of charmless $B^{\pm}$ decays
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ABSTRACT: The charmless threebody decay modes $B^{\pm} \rightarrow K^{\pm} \pi^{+} \pi^{}$, $B^{\pm} \rightarrow K^{\pm} K^{+} K^{}$, $B^{\pm} \rightarrow \pi^{\pm} K^{+} K^{}$ and $B^{\pm} \rightarrow \pi^{\pm} \pi^{+} \pi^{}$ are reconstructed using data, corresponding to an integrated luminosity of 3.0\;$\mbox{\,fb}^{1}$, collected by the LHCb detector. The inclusive $C\!P$ asymmetries of these modes are measured to be $$ A_{C\!P}(B^{\pm} \rightarrow K^{\pm} \pi^{+} \pi^{})= +0.025 \pm 0.004 \pm 0.004 \pm 0.007 \\ A_{C\!P}(B^{\pm} \rightarrow K^{\pm} K^{+} K^{}) = 0.036 \pm 0.004 \pm 0.002 \pm 0.007 \\ A_{C\!P}(B^{\pm} \rightarrow \pi^{\pm} \pi^{+} \pi^{})= +0.058 \pm 0.008 \pm 0.009 \pm 0.007 \\ A_{C\!P}(B^{\pm} \rightarrow \pi^{\pm} K^{+} K^{})= 0.123 \pm 0.017 \pm 0.012 \pm 0.007 $$ %% where the first uncertainty is statistical, the second systematic, and the third is due to the $C\!P$ asymmetry of the $B^{\pm} \rightarrow J/\psi K^{\pm}$ reference mode. The distributions of these asymmetries are also studied as functions of position in the Dalitz plot and suggest contributions from rescattering and resonance interference processes. 
Article: Measurement of the forward $W$ boson crosssection in $pp$ collisions at $\sqrt{s} = 7 {\rm \, TeV}$
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ABSTRACT: A measurement of the inclusive $W \to \mu\nu$ production crosssection using data from $pp$ collisions at a centreofmass energy of $\sqrt{s} = 7 {\rm \, TeV}$ is presented. The analysis is based on an integrated luminosity of about $1.0 {\rm \, fb}^{1}$ recorded with the LHCb detector. Results are reported for muons with a transverse momentum greater than $20 {\rm \, Ge\kern 0.1em V\!/}c$ and pseudorapidity between 2.0 and 4.5. The $W^{+}$ and $W^{}$ production crosssections are measured to be $$\sigma_{W^{+} \to \mu^{+}\nu} = 861.0 \pm 2.0 \pm 11.2 \pm 14.7 {\rm \, pb},$$ $$\sigma_{W^{} \to \mu^{}\overline{\nu}} = 675.8 \pm 1.9 \pm 8.8 \pm 11.6 {\rm \, pb},$$ where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity determination. Crosssection ratios and differential distributions as functions of the muon pseudorapidity are also presented. The ratio of $W^{+}$ to $W^{}$ crosssections in the same fiducial kinematic region is determined to be $$\frac{\sigma_{W^{+} \to \mu^{+}\nu}}{\sigma_{W^{} \to \mu^{}\overline{\nu}}} = 1.274 \pm 0.005 \pm 0.009,$$ where the uncertainties are statistical and systematic, respectively. Results are in good agreement with theoretical predictions at nexttonexttoleading order in perturbative quantum chromodynamics.  [Show abstract] [Hide abstract]
ABSTRACT: The determination of track reconstruction efficiencies at LHCb using $J/\psi\rightarrow\mu^{+}\mu^{}$ decays is presented. Efficiencies above $95\%$ are found for the data taking periods in 2010, 2011, and 2012. The ratio of the track reconstruction efficiency of muons in data and simulation is compatible with unity and measured with an uncertainty of $0.8\,\%$ for data taking in 2010, and at a precision of $0.4\,\%$ for data taking in 2011 and 2012. For hadrons an additional $1.4\,\%$ uncertainty due to material interactions is assumed. This result is crucial for accurate cross section and branching fraction measurements in LHCb.  [Show abstract] [Hide abstract]
ABSTRACT: A baryonic decay of the $B_c^+$ meson, $B_c^+\to J/\psi p\overline{p}\pi^+$, is observed for the first time, with a significance of $7.3$ standard deviations, in $pp$ collision data collected with the LHCb detector and corresponding to an integrated luminosity of $3.0$ fb$^{1}$ taken at centerofmass energies of $7$ and $8$ $\mathrm{TeV}$. With the $B_c^+\to J/\psi \pi^+$ decay as normalization channel, the ratio of branching fractions is measured to be \begin{equation*} \frac{\mathcal{B}(B_c^+\to J/\psi p\overline{p}\pi^+)}{\mathcal{B}(B_c^+\to J/\psi \pi^+)} = 0.143^{\,+\,0.039}_{\,\,0.034}\,(\mathrm{stat})\pm0.013\,(\mathrm{syst}). \end{equation*} The mass of the $B_c^+$ meson is determined as $M(B_c^+)=6274.0\pm1.8\,(\mathrm{stat})\pm0.4\,(\mathrm{syst})\,\mathrm{MeV}/c^2$, using the $B_c^+\to J/\psi p\overline{p}\pi^+$ channel. 
Article: Measurement of the B0barB0 and BsbarBs production asymmetries in pp collisions at sqrt(s)=7 TeV
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ABSTRACT: The B0barB0 and BsbarBs production asymmetries, AP(B0) and AP(Bs), are measured by means of a timedependent analysis of B0 > J/\psi K*0, B0 > D pi+ and Bs > Ds pi+ decays, using a data sample corresponding to an integrated luminosity of 1.0 fb^{1}, collected by LHCb in pp collisions at a centreofmass energy of 7 TeV. The measurements are performed as a function of transverse momentum and pseudorapidity of the B0 and Bs mesons within the LHCb acceptance. The production asymmetries, integrated over pT and eta in the range 4 < pT< 30 GeV/c and 2.5<eta<4.5, are determined to be AP(B0) = (0.35 +/ 0.76 +/ 0.28)% and AP(Bs) = (1.09 +/ 2.61 +/ 0.66)%, where the first uncertainties are statistical and the second systematic.  [Show abstract] [Hide abstract]
ABSTRACT: The resonant substructure of $B_s^0 \rightarrow \overline{D}^0 K^ \pi^+$ decays is studied with the Dalitz plot analysis technique. The study is based on a data sample corresponding to an integrated luminosity of $3.0\,{\rm fb}^{1}$ of $pp$ collision data recorded by LHCb. A structure at $m(\overline{D}^0 K^) \approx 2.86 {\rm GeV}/c^2$ is found to be an admixture of spin1 and spin3 resonances. The masses and widths of these states and of the $D^*_{s2}(2573)^$ meson are measured, as are the complex amplitudes and fit fractions for all the $\overline{D}^0 K^$ and $K^\pi^+$ components included in the amplitude model. In addition, the $D^*_{s2}(2573)^$ resonance is confirmed to be spin2.  [Show abstract] [Hide abstract]
ABSTRACT: Measurements of the branching fractions of $B^0_{(s)} \to K^{*\pm}K^\mp$ and $B^0_{(s)} \to K^{*\pm}\pi^\mp$ decays are performed using a data sample corresponding to $1.0 \ {\rm fb}^{1}$ of protonproton collision data collected with the LHCb detector at a centreofmass energy of $7\mathrm{\,TeV}$, where the $K^{*\pm}$ mesons are reconstructed in the $K^0_{\rm S}\pi^\pm$ final state. The first observation of the $B^0_s \to K^{*\pm}K^\mp$ decay and the first evidence for the $B^0_s \to K^{*}\pi^+$ decay are reported with branching fractions \begin{eqnarray} {\cal B}\left(B^0_s \to K^{*\pm}K^\mp\right) & = & \left( 12.7\pm1.9\pm1.9 \right) \times 10^{6} \, , \\ {\cal B}\left(B^0_s \to K^{*}\pi^+\right) & = & ~\left( 3.3\pm1.1\pm0.5 \right) \times 10^{6} \, , \end{eqnarray} where the first uncertainties are statistical and the second are systematic. In addition, an upper limit of ${\cal B}\left(B^0 \to K^{*\pm}K^\mp\right) < 0.4 \ (0.5) \times 10^{6}$ is set at $90\,\% \ (95\,\%)$ confidence level.  [Show abstract] [Hide abstract]
ABSTRACT: The resonant substructure of $B_s^0 \rightarrow \overline{D}^0 K^ \pi^+$ decays is studied using a data sample corresponding to an integrated luminosity of $3.0\,{\rm fb}^{1}$ of $pp$ collision data recorded by the LHCb detector. An excess at $m(\overline{D}^0 K^) \approx 2.86 {\rm GeV}/c^2$ is found to be an admixture of spin1 and spin3 resonances. Therefore the $D^*_{sJ}(2860)^$ state previously observed in inclusive $e^+e^ \rightarrow \overline{D}^0 K^ X$ and $pp \rightarrow \overline{D}^0 K^ X$ processes consists of at least two particles. This is the first observation of a heavy flavoured spin3 resonance, and the first time that any spin3 particle has been seen to be produced in $B$ decays. The masses and widths of the new states and of the $D^*_{s2}(2573)^$ meson are measured, giving the most precise determinations to date.  [Show abstract] [Hide abstract]
ABSTRACT: A modeldependent amplitude analysis of $B^{\pm} \rightarrow D K^{\pm}$ with $D \rightarrow K_S^0 \pi^+ \pi^$ decays is performed using protonproton collision data, corresponding to an integrated luminosity of $1$ fb$^{1}$, recorded by LHCb at a centreofmass energy of $7$ TeV in $2011$. Values of the $CP$ violation observables $x_{\pm}$ and $y_{\pm}$, which are sensitive to the CKM angle $\gamma$, are measured to be \begin{align*} x_ &= +0.027 \pm 0.044 ^{+0.010}_{0.008} \pm 0.001, \\ y_ &= +0.013 \pm 0.048 ^{+0.009}_{0.007} \pm 0.003, \\ x_+ &= 0.084 \pm 0.045 \pm 0.009 \pm 0.005, \\ y_+ &= 0.032 \pm 0.048 ^{+0.010}_{0.009} \pm 0.008, \end{align*} where the first uncertainty is statistical, the second systematic and the third arises from the uncertainty of the $D \rightarrow K_S^0 \pi^+ \pi^$ amplitude model. The value of $\gamma$ is determined to be $(84^{+49}_{42})^\circ$, including all sources of uncertainty. Neutral $D$ meson mixing is found to have negligible effect.  [Show abstract] [Hide abstract]
ABSTRACT: We present a measurement of the ratio of the Bs meson lifetime, in the flavorspecific decay to $D_s^+\pi^$, to that of the B0 meson. The pp collision data used correspond to an integrated luminosity of 1/fb, collected with the LHCb detector, at a centerofmass energy of 7 TeV. Combining our measured value of 1.010 +/ 0.010 +/ 0.008 for this ratio with the known lifetime, we determine the flavorspecific Bs lifetime to be tau(Bs) = 1.535 +/ 0.015 +/ 0.014 ps, where the uncertainties are statistical and systematic, respectively. This is the most precise measurement to date, and is consistent with previous measurements and theoretical predictions.  [Show abstract] [Hide abstract]
ABSTRACT: A search is performed for the central exclusive production of pairs of charmonia produced in protonproton collisions. Using data corresponding to an integrated luminosity of $3{\rm\ fb}^{1}$ collected at centreofmass energies of 7 and 8 TeV, $J/\psi J/\psi$ and $J/\psi\psi(2S)$ pairs are observed, which have been produced in the absence of any other activity inside the LHCb acceptance that is sensitive to charged particles in the pseudorapidity ranges $(3.5,1.5)$ and $(1.5,5.0)$. Searches are also performed for pairs of Pwave charmonia and limits are set on their production. The crosssections for these processes, where the dimeson system has a rapidity between 2.0 and 4.5, are measured to be $$ \begin{array}{rl} \sigma^{J/\psi J/\psi} &= 58\pm10{(\rm stat)} \pm 6{(\rm syst)} {\rm\ pb} , \\ \sigma^{J/\psi\psi(2S)} &= 63 ^{+27}_{18}{(\rm stat)}\pm 10{(\rm syst)} {\rm\ pb} , \\ \sigma^{\psi(2S)\psi(2S)} &< 237 {\rm\ pb}, \\ \sigma^{\chi_{c0}\chi_{c0}} &< 69 {\rm\ nb}, \\ \sigma^{\chi_{c1}\chi_{c1}} &< 45 {\rm\ pb}, \\ \sigma^{\chi_{c2}\chi_{c2}} &< 141 {\rm\ pb}, \\ \end{array} $$ where the upper limits are set at the 90% confidence level. The measured $J/\psi J/\psi$ and $J/\psi\psi(2S)$ crosssections are consistent with theoretical expectations.Journal of Physics G Nuclear and Particle Physics 07/2014; 41(11). DOI:10.1088/09543899/41/11/115002 · 2.84 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Threebody $B^+\to p \overline p K^+$ and $B^+\to p \overline p \pi^+$ decays are studied using a data sample corresponding to an integrated luminosity of 3.0 $fb^{1}$ collected by the LHCb experiment in protonproton collisions at centerofmass energies of $7$ and $8$ TeV. Evidence of CP violation in the $B^+\to p \overline p K^+$ decay is found in regions of the phase space, representing the first measurement of this kind for a final state containing baryons. Measurements of the forwardbackward asymmetry of the light meson in the $p\overline p$ rest frame yield $A_{\mathrm{FB}}(p \overline p K^+,~m_{p\overline p}<2.85\mathrm{\,Ge\kern 0.1em V\!/}c^2)=0.495\pm0.012~(\mathrm{stat})\pm0.007~(\mathrm{syst})$ and $A_{\mathrm{FB}}(p\overline p \pi^+,~m_{p\overline p}<2.85\mathrm{\,Ge\kern 0.1em V\!/}c^2)=0.409\pm0.033~(\mathrm{stat})\pm0.006~(\mathrm{syst})$. In addition, the branching fraction of the decay $B^+\to\kern 0.1em\overline{\kern 0.1em\Lambda}(1520)p$ is measured to be $\mathcal{B}(B^+ \to \kern 0.1em\overline{\kern 0.1em\Lambda}(1520)p)=(3.15\pm0.48~(\mathrm{stat})\pm0.07~(\mathrm{syst})\pm0.26~(\mathrm{BF}))\times 10^{7}$, where BF denotes the uncertainty on secondary branching fractions. 
Article: Measurement of the ratio of $B_c^+$ branching fractions to $J/\psi\pi^+$ and $J/\psi\mu^+\nu_\mu$
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ABSTRACT: The first measurement that relates semileptonic and hadronic decay rates of the $B_c^+$ meson is performed using protonproton collision data corresponding to 1.0 fb$^{1}$ of integrated luminosity collected with the LHCb detector. The measured value of the ratio of branching fractions, ${\cal B}(B_c^+ \to J/\psi \pi^+)/{\cal B}(B_c^+\to J/\psi\mu^+\nu_\mu)=0.0469 \pm 0.0028 (stat.) \pm 0.0046 (syst.)$, is at the lower end of available theoretical predictions.  [Show abstract] [Hide abstract]
ABSTRACT: A measurement of the decay time dependent $CP$violating asymmetry in $B_s^0 \to \phi\phi$ decays is presented, along with measurements of the $T$odd tripleproduct asymmetries. In this decay channel, the $CP$violating weak phase arises from the interference between $B_s^0$$\overline{B}_s^0$ mixing and the loopinduced decay amplitude. Using a sample of protonproton collision data corresponding to an integrated luminosity of $3.0\, fb^{1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 \to \phi\phi$ decays is obtained. The $CP$violating phase is measured to be ${\phi_s =0.17\pm0.15\mathrm{\,(stat)}\pm0.03\mathrm{\,(syst)}}$ rad. The tripleproduct asymmetries are measured to be ${A_U=0.003\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$ and ${A_V=0.017\pm0.017\mathrm{\,(stat)}\pm0.006\mathrm{\,(syst)}}$. Results are consistent with the hypothesis of $CP$ conservation.  [Show abstract] [Hide abstract]
ABSTRACT: Measurements of the effective lifetimes in the $B_{s}^{0} \rightarrow K^{+}K^{}$, $B^{0} \rightarrow K^{+}\pi^{}$ and $B_{s}^{0} \rightarrow \pi^{+}K^{}$ decays are presented using $1.0~\mathrm{fb^{1}}$ of $pp$ collision data collected at a centreofmass energy of 7 TeV by the LHCb experiment. The analysis uses a datadriven approach to correct for the decay time acceptance. The measured effective lifetimes are $\tau_{B_{s}^{0} \rightarrow K^{+}K^{}}$ = $1.407~\pm~0.016~\pm~0.007~\mathrm{ps}$, $\tau_{B^{0} \rightarrow K^{+}\pi^{}}$ = $1.524~\pm~0.011~\pm~0.004~\mathrm{ps}$, $\tau_{B_{s}^{0} \rightarrow \pi^{+}K^{}}$ = $1.60~\pm~0.06~\pm~0.01~\mathrm{ps}$. This is the most precise determination to date of the effective lifetime in the $B_{s}^{0} \rightarrow K^{+}K^{}$ decay and provides constraints on contributions from physics beyond the Standard Model to the $B_{s}^{0}$ mixing phase and the width difference $\Delta\Gamma_{s}$.  [Show abstract] [Hide abstract]
ABSTRACT: A measurement of the ratio of the branching fractions of the $B^{+}\rightarrow K^{+}\mu^{+}\mu^{}$ and $B^{+}\rightarrow K^{+}e^{+}e^{}$ decays is presented using protonproton collision data, corresponding to an integrated luminosity of 3.0 fb$^{1}$, recorded with the LHCb experiment at centerofmass energies of 7 and 8 $\mathrm{\,Te\kern 0.1em V}$. The value of the ratio of branching fractions for the dilepton invariant mass squared range $1<q^{2}<6\mathrm{\,Ge\kern 0.1em V^2\!/}c^4$ is measured to be $0.745^{+0.090}_{0.074}\mathrm{\,(stat)}\,\pm0.036\mathrm{\,(syst)}$. This value is the most precise measurement of the ratio of branching fractions to date and is compatible with the SM prediction within $2.6$ standard deviations.  Physical Review D 06/2014; 89(11). DOI:10.1103/PhysRevD.89.112004 · 4.86 Impact Factor
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ABSTRACT: A search for \CP violation in Cabibbosuppressed $D^{\pm}\rightarrow K^0_{\mathrm{S}} K^{\pm}$ and $D^{\pm}_{s}\rightarrow K^0_{\mathrm{S}} \pi^{\pm}$ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of 3~fb$^{1}$, recorded by the LHCb experiment. The individual $CP$violating asymmetries are measured to be \begin{eqnarray*} \mathcal{A}_{CP}^{D^{\pm}\rightarrow K^0_{\mathrm{S}} K^{\pm}} & = & (+0.03 \pm 0.17 \pm 0.14) \% \mathcal{A}_{CP}^{D^{\pm}_{s}\rightarrow K^0_{\mathrm{S}} \pi^{\pm}} & = & (+0.38 \pm 0.46 \pm 0.17) \%, \end{eqnarray*} assuming that $CP$ violation in the Cabibbofavoured decays is negligible. A combination of the measured asymmetries for the four decay modes $D^{\pm}_{(s)}\rightarrow K^0_{\mathrm{S}} K^{\pm}$ and $D^{\pm}_{(s)}\rightarrow K^0_{\mathrm{S}} \pi^{\pm}$ gives the sum \[ \mathcal{A}_{CP}^{D^{\pm}\rightarrow K^0_{\mathrm{S}} K^{\pm}} + \mathcal{A}_{CP}^{D^{\pm}_{s}\rightarrow K^0_{\mathrm{S}} \pi^{\pm}} = (+0.41 \pm 0.49 \pm 0.26) \%. \] In all cases, the first uncertainties are statistical and the second systematic. The results represent the most precise measurements of these asymmetries to date and show no evidence for CP violation.  [Show abstract] [Hide abstract]
ABSTRACT: Using a protonproton collision data sample corresponding to an integrated luminosity of 3 fb$^{1}$ collected by LHCb at centerofmass energies of 7 and 8 TeV, about 3800 $\Xi_b^0\to\Xi_c^+\pi^$, $\Xi_c^+\to pK^\pi^+$ signal decays are reconstructed. From this sample, the first measurement of the $\Xi_b^0$ baryon lifetime is made, relative to that of the $\Lambda_b^0$ baryon. The mass differences $M(\Xi_b^0)M(\Lambda_b^0)$ and $M(\Xi_c^+)M(\Lambda_c^+)$ are also measured with precision more than four times better than the current world averages. The resulting values are $\frac{\tau_{\Xi_b^0}}{\tau_{\Lambda_b^0}} = 1.006\pm0.018\pm0.010$, $M(\Xi_b^0)  M(\Lambda_b^0) = 172.44\pm0.39\pm0.17 MeV/c^2$, $M(\Xi_c^+)  M(\Lambda_c^+) = 181.51\pm0.14\pm0.10 MeV/c^2$, where the first uncertainty is statistical and the second is systematic. The relative rate of $\Xi_b^0$ to $\Lambda_b^0$ baryon production is measured to be $\frac{f_{\Xi_b^0}}{f_{\Lambda_b^0}}\frac{{\cal{B}}(\Xi_b^0\to\Xi_c^+\pi^)}{{\cal{B}}(\Lambda_b^0\to\Lambda_c^+\pi^)}\frac{{\cal{B}}(\Xi_c^+\to pK^\pi^+)}{{\cal{B}}(\Lambda_c^+\to pK^\pi^+)} = (1.88\pm0.04\pm0.03)\times10^{2}$, where the first factor is the ratio of fragmentation fractions, $b\to\Xi_b^0$ relative to $b\to\Lambda_b^0$. Relative production rates as functions of transverse momentum and pseudorapidity are also presented.Physical Review Letters 05/2014; 113(3). DOI:10.1103/PhysRevLett.113.032001 · 7.73 Impact Factor
Publication Stats
4k  Citations  
1,211.01  Total Impact Points  
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Institutions

1988–2010

Technische Universität Dortmund
 Faculty of Physics
Dortmund, North RhineWestphalia, Germany


2004

Technische Universität Dresden
Dresden, Saxony, Germany


1996

University of Hamburg
Hamburg, Hamburg, Germany


1995

Deutsches ElektronenSynchrotron
Hamburg, Hamburg, Germany


1994

McGill University
Montréal, Quebec, Canada


1986–1994

Universität Heidelberg
 Institute of Physics
Heidelburg, BadenWürttemberg, Germany


1992

Lund University
Lund, Skåne, Sweden


1991–1992

Carleton University
Ottawa, Ontario, Canada
