Environmentally friendly and energy-efficient ways to produce ammonia are essential to meet globa... more Environmentally friendly and energy-efficient ways to produce ammonia are essential to meet global food demands. Here, a new approach for ammonia production at nominally ambient conditions is introduced. As proof of concept, ammonia is synthesized mechanocatalytically by ball milling titanium in a continuous gas flow. The ammonia synthesis reaction is proposed to follow a transient Mars− van Krevelen mechanism under mechanically activated conditions, where molecular nitrogen incorporation into the titanium lattice and titanium nitride hydrogenation occur in thermodynamically distinct environments. X-ray powder diffraction and X-ray absorption spectroscopy confirm the formation of titanium nitride from titanium and N 2. The reactivity of nitrided titanium supports that lattice nitrogen plays a role in ammonia formation. The in situ formed titanium nitride is catalytically active, and the nitride regeneration reaction is determined to be the ratelimiting step. A preliminary technoeconomic analysis shows that this approach could be feasible for distributed ammonia production.
Der fortschreitende Klimawandel, verändertes Umweltbewusstsein und sich verringernde Kohle-, Öl- ... more Der fortschreitende Klimawandel, verändertes Umweltbewusstsein und sich verringernde Kohle-, Öl- und Gasvorräte machen die Erschließung neuer Rohstoffquellen nötig. CO₂ kommt hier eine besondere Rolle zu, da es sowohl für einen Großteil des Klimawandels verantwortlich ist als auch eine Kohlenstoffquelle mit weltweiter Verfügbarkeit darstellt. In einem ersten Schritt konnte ein Ceroxidkatalysator entwickelt werden, der eine gute Performance in der Diethylcarbonatsynthese zeigt. Hierbei ist eine pH-Wert- und temperaturgesteuerte Katalysatorfällung, als auch die Beachtung thermodynamischer Limitierungen in der Carbonatsynthese notwendig. Die größte Herausforderung in der Diethylcarbonatsynthese stellt dabei die Gleichgewichtslimitierung auf Seite der Edukte dar. Einzig die Entfernung von Wasser aus dem Gleichgewicht erweist sich als zweckmäßig. Zum Einsatz kommen hier organische und anorganische Membranen, welche jedoch nicht langzeitstabil gegenüber CO₂ sind, sodass ein erfolgreicher ...
The CP-violating weak phase φ s of the B 0 s meson and the decay width difference ∆Γ s of the B 0... more The CP-violating weak phase φ s of the B 0 s meson and the decay width difference ∆Γ s of the B 0 s light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of B 0 s → J/ψ φ(1020) → µ + µ − K + K − decays. The analysed data set corresponds to an integrated luminosity of 19.7 fb −1 collected in pp collisions at a centre-of-mass energy of 8 TeV. A total of 49 200 reconstructed B 0 s decays are used to extract the values of φ s and ∆Γ s by performing a time-dependent and flavourtagged angular analysis of the µ + µ − K + K − final state. The weak phase is measured to be φ s = −0.075 ± 0.097 (stat) ± 0.031 (syst) rad, and the decay width difference is ∆Γ s = 0.095 ± 0.013 (stat) ± 0.007 (syst) ps −1 .
A search is presented for quark contact interactions and extra spatial dimensions in proton-proto... more A search is presented for quark contact interactions and extra spatial dimensions in proton-proton collisions at √ s = 8 TeV using dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7 fb −1 collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-toleading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7) TeV for destructive (constructive) interference at 95% confidence level. Lower limits between 5.9 and 8.4 TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed-Dimopoulos-Dvali model of extra spatial dimensions.
The European physical journal. C, Particles and fields
Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-pr... more Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8[Formula: see text] are presented. Candidate events for the leptonic decay mode [Formula: see text], where [Formula: see text] denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6)[Formula: see text] at 7 (8)[Formula: see text] collected with the CMS experiment. The measured cross sections, [Formula: see text] at 7[Formula: see text], and [Formula: see text] at 8[Formula: see text], are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the [Formula: see text][Formula: see text] final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with ...
A measurement of the inclusive ZZ production cross section and constraints on anomalous triple ga... more A measurement of the inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at √ s = 8 TeV are presented. The analysis is based on a data sample, corresponding to an integrated luminosity of 19.6 fb −1 , collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ → , where = e, µ and = e, µ, τ. The measured total cross section σ(pp → ZZ) = 7.7 ± 0.5 (stat) +0.5 −0.4 (syst) ± 0.4 (theo) ± 0.2 (lumi) pb, for both Z bosons produced in the mass range 60 < m Z < 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings at the 95% confidence level: −0.004 < f Z 4 < 0.004, −0.004 < f Z 5 < 0.004, −0.005 < f γ 4 < 0.005, and −0.005 < f γ 5 < 0.005.
Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb co... more Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies The CMS Collaboration *
The normalised differential top quark-antiquark production cross section is measured as a functio... more The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0 fb −1. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the tt production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
View the article online for updates and enhancements. Related content Commissioning and performan... more View the article online for updates and enhancements. Related content Commissioning and performance of the CMS silicon strip tracker with cosmic ray muons CMS Collaboration-Commissioning and performance of the CMS pixel tracker with cosmic ray muons CMS Collaboration
A search is reported for the standard model Higgs boson in the H → ZZ → + − τ + τ − decay mode, w... more A search is reported for the standard model Higgs boson in the H → ZZ → + − τ + τ − decay mode, where = µ or e, in proton-proton collisions at √ s = 7 TeV, corresponding to an integrated luminosity of 4.7 fb −1 collected with the CMS detector at the LHC. No evidence is found for a significant deviation from the background expectation. An upper limit four to twelve times larger than the predicted value is set at 95% confidence level for the product of the standard model Higgs boson production cross section and decay branching fraction in the mass range 190 < m H < 600 GeV.
Results are presented from a search for the pair-production of heavy quarks, QQ, that decay exclu... more Results are presented from a search for the pair-production of heavy quarks, QQ, that decay exclusively into a top quark and a W or Z boson. The search is performed using a sample of proton-proton collisions at √ s = 7 TeV corresponding to an integrated luminosity of 5.0 fb −1 , collected by the Compact Muon Solenoid experiment. The signal region is defined using a sample of events containing one electron or muon, missing transverse momentum, and at least four jets with large transverse momenta, where one jet is likely to originate from the decay of a bottom quark. No significant excess of events is observed with respect to the standard model expectations. Assuming a strong pair-production mechanism, quark masses below 675 (625) GeV decaying into tW (tZ) are excluded at the 95% confidence level.
Measurements of the differential cross sections for the production of exactly four jets in proton... more Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum p T and pseudorapidity η, together with the correlations in azimuthal angle and the p T balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb −1. The cross section for exactly four jets, with two hard jets of p T > 50 GeV each, together with two jets of p T > 20 GeV each, within jηj < 4.7 is measured to be σ ¼ 330 AE 5ðstat:Þ AE 45ðsyst:Þ nb. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data.
The cross section for dijet production in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV is p... more The cross section for dijet production in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV is presented as a function of, a variable that approximates the fractional momentum loss of the scattered proton in singlediffractive events. The analysis is based on an integrated luminosity of 2:7 nb À1 collected with the CMS detector at the LHC at low instantaneous luminosities, and uses events with jet transverse momentum of at least 20 GeV. The dijet cross section results are compared to the predictions of diffractive and nondiffractive models. The low-data show a significant contribution from diffractive dijet production, observed for the first time at the LHC. The associated rapidity gap survival probability is estimated.
A search is performed for pair-produced spin-3/2 excited top quarks (t * t *), each decaying to a... more A search is performed for pair-produced spin-3/2 excited top quarks (t * t *), each decaying to a top quark and a gluon. The search uses data collected with the CMS detector from pp collisions at a center-of-mass energy of √ s = 8 TeV, selecting events that have a single isolated muon or electron, an imbalance in transverse momentum, and at least six jets, of which one must be compatible with originating from the fragmentation of a b quark. The data, corresponding to an integrated luminosity of 19.5 fb −1 , show no significant excess over standard model predictions, and provide a lower limit of 803 GeV at 95% confidence on the mass of the spin-3/2 t * quark in an extension of the Randall-Sundrum model, assuming a 100% branching fraction of its decay into a top quark and a gluon. This is the first search for a spin-3/2 excited top quark performed at the LHC.
Measurements of the differential and double-differential Drell-Yan cross sections are presented u... more Measurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5 (4.8) fb−1 in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at $ \sqrt{s} $ = 7 TeV. The measured inclusive cross section in the Z-peak region (60–120 GeV) is σ(ℓℓ) = 986.4 ± 0.6 (stat.) ± 5.9 (exp. syst.) ± 21.7 (th. syst.) ± 21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections dσ/dm for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section d2σ/dm d|y| in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading o...
Environmentally friendly and energy-efficient ways to produce ammonia are essential to meet globa... more Environmentally friendly and energy-efficient ways to produce ammonia are essential to meet global food demands. Here, a new approach for ammonia production at nominally ambient conditions is introduced. As proof of concept, ammonia is synthesized mechanocatalytically by ball milling titanium in a continuous gas flow. The ammonia synthesis reaction is proposed to follow a transient Mars− van Krevelen mechanism under mechanically activated conditions, where molecular nitrogen incorporation into the titanium lattice and titanium nitride hydrogenation occur in thermodynamically distinct environments. X-ray powder diffraction and X-ray absorption spectroscopy confirm the formation of titanium nitride from titanium and N 2. The reactivity of nitrided titanium supports that lattice nitrogen plays a role in ammonia formation. The in situ formed titanium nitride is catalytically active, and the nitride regeneration reaction is determined to be the ratelimiting step. A preliminary technoeconomic analysis shows that this approach could be feasible for distributed ammonia production.
Der fortschreitende Klimawandel, verändertes Umweltbewusstsein und sich verringernde Kohle-, Öl- ... more Der fortschreitende Klimawandel, verändertes Umweltbewusstsein und sich verringernde Kohle-, Öl- und Gasvorräte machen die Erschließung neuer Rohstoffquellen nötig. CO₂ kommt hier eine besondere Rolle zu, da es sowohl für einen Großteil des Klimawandels verantwortlich ist als auch eine Kohlenstoffquelle mit weltweiter Verfügbarkeit darstellt. In einem ersten Schritt konnte ein Ceroxidkatalysator entwickelt werden, der eine gute Performance in der Diethylcarbonatsynthese zeigt. Hierbei ist eine pH-Wert- und temperaturgesteuerte Katalysatorfällung, als auch die Beachtung thermodynamischer Limitierungen in der Carbonatsynthese notwendig. Die größte Herausforderung in der Diethylcarbonatsynthese stellt dabei die Gleichgewichtslimitierung auf Seite der Edukte dar. Einzig die Entfernung von Wasser aus dem Gleichgewicht erweist sich als zweckmäßig. Zum Einsatz kommen hier organische und anorganische Membranen, welche jedoch nicht langzeitstabil gegenüber CO₂ sind, sodass ein erfolgreicher ...
The CP-violating weak phase φ s of the B 0 s meson and the decay width difference ∆Γ s of the B 0... more The CP-violating weak phase φ s of the B 0 s meson and the decay width difference ∆Γ s of the B 0 s light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of B 0 s → J/ψ φ(1020) → µ + µ − K + K − decays. The analysed data set corresponds to an integrated luminosity of 19.7 fb −1 collected in pp collisions at a centre-of-mass energy of 8 TeV. A total of 49 200 reconstructed B 0 s decays are used to extract the values of φ s and ∆Γ s by performing a time-dependent and flavourtagged angular analysis of the µ + µ − K + K − final state. The weak phase is measured to be φ s = −0.075 ± 0.097 (stat) ± 0.031 (syst) rad, and the decay width difference is ∆Γ s = 0.095 ± 0.013 (stat) ± 0.007 (syst) ps −1 .
A search is presented for quark contact interactions and extra spatial dimensions in proton-proto... more A search is presented for quark contact interactions and extra spatial dimensions in proton-proton collisions at √ s = 8 TeV using dijet angular distributions. The search is based on a data set corresponding to an integrated luminosity of 19.7 fb −1 collected by the CMS detector at the CERN LHC. Dijet angular distributions are found to be in agreement with the perturbative QCD predictions that include electroweak corrections. Limits on the contact interaction scale from a variety of models at next-toleading order in QCD corrections are obtained. A benchmark model in which only left-handed quarks participate is excluded up to a scale of 9.0 (11.7) TeV for destructive (constructive) interference at 95% confidence level. Lower limits between 5.9 and 8.4 TeV on the scale of virtual graviton exchange are extracted for the Arkani-Hamed-Dimopoulos-Dvali model of extra spatial dimensions.
The European physical journal. C, Particles and fields
Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-pr... more Measurements of the [Formula: see text][Formula: see text] production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8[Formula: see text] are presented. Candidate events for the leptonic decay mode [Formula: see text], where [Formula: see text] denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6)[Formula: see text] at 7 (8)[Formula: see text] collected with the CMS experiment. The measured cross sections, [Formula: see text] at 7[Formula: see text], and [Formula: see text] at 8[Formula: see text], are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the [Formula: see text][Formula: see text] final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with ...
A measurement of the inclusive ZZ production cross section and constraints on anomalous triple ga... more A measurement of the inclusive ZZ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at √ s = 8 TeV are presented. The analysis is based on a data sample, corresponding to an integrated luminosity of 19.6 fb −1 , collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes ZZ → , where = e, µ and = e, µ, τ. The measured total cross section σ(pp → ZZ) = 7.7 ± 0.5 (stat) +0.5 −0.4 (syst) ± 0.4 (theo) ± 0.2 (lumi) pb, for both Z bosons produced in the mass range 60 < m Z < 120 GeV, is consistent with standard model predictions. Differential cross sections are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZγ couplings at the 95% confidence level: −0.004 < f Z 4 < 0.004, −0.004 < f Z 5 < 0.004, −0.005 < f γ 4 < 0.005, and −0.005 < f γ 5 < 0.005.
Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb co... more Long-range two-particle correlations of strange hadrons with charged particles in pPb and PbPb collisions at LHC energies The CMS Collaboration *
The normalised differential top quark-antiquark production cross section is measured as a functio... more The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC with the CMS detector. The measurement is performed in both the dilepton and lepton+jets decay channels using data corresponding to an integrated luminosity of 5.0 fb −1. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the tt production is determined as a function of the additional jet multiplicity in the lepton+jets channel. Furthermore, the fraction of events with no additional jets is measured in the dilepton channel, as a function of the threshold on the jet transverse momentum. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
View the article online for updates and enhancements. Related content Commissioning and performan... more View the article online for updates and enhancements. Related content Commissioning and performance of the CMS silicon strip tracker with cosmic ray muons CMS Collaboration-Commissioning and performance of the CMS pixel tracker with cosmic ray muons CMS Collaboration
A search is reported for the standard model Higgs boson in the H → ZZ → + − τ + τ − decay mode, w... more A search is reported for the standard model Higgs boson in the H → ZZ → + − τ + τ − decay mode, where = µ or e, in proton-proton collisions at √ s = 7 TeV, corresponding to an integrated luminosity of 4.7 fb −1 collected with the CMS detector at the LHC. No evidence is found for a significant deviation from the background expectation. An upper limit four to twelve times larger than the predicted value is set at 95% confidence level for the product of the standard model Higgs boson production cross section and decay branching fraction in the mass range 190 < m H < 600 GeV.
Results are presented from a search for the pair-production of heavy quarks, QQ, that decay exclu... more Results are presented from a search for the pair-production of heavy quarks, QQ, that decay exclusively into a top quark and a W or Z boson. The search is performed using a sample of proton-proton collisions at √ s = 7 TeV corresponding to an integrated luminosity of 5.0 fb −1 , collected by the Compact Muon Solenoid experiment. The signal region is defined using a sample of events containing one electron or muon, missing transverse momentum, and at least four jets with large transverse momenta, where one jet is likely to originate from the decay of a bottom quark. No significant excess of events is observed with respect to the standard model expectations. Assuming a strong pair-production mechanism, quark masses below 675 (625) GeV decaying into tW (tZ) are excluded at the 95% confidence level.
Measurements of the differential cross sections for the production of exactly four jets in proton... more Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum p T and pseudorapidity η, together with the correlations in azimuthal angle and the p T balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of 36 pb −1. The cross section for exactly four jets, with two hard jets of p T > 50 GeV each, together with two jets of p T > 20 GeV each, within jηj < 4.7 is measured to be σ ¼ 330 AE 5ðstat:Þ AE 45ðsyst:Þ nb. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data.
The cross section for dijet production in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV is p... more The cross section for dijet production in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV is presented as a function of, a variable that approximates the fractional momentum loss of the scattered proton in singlediffractive events. The analysis is based on an integrated luminosity of 2:7 nb À1 collected with the CMS detector at the LHC at low instantaneous luminosities, and uses events with jet transverse momentum of at least 20 GeV. The dijet cross section results are compared to the predictions of diffractive and nondiffractive models. The low-data show a significant contribution from diffractive dijet production, observed for the first time at the LHC. The associated rapidity gap survival probability is estimated.
A search is performed for pair-produced spin-3/2 excited top quarks (t * t *), each decaying to a... more A search is performed for pair-produced spin-3/2 excited top quarks (t * t *), each decaying to a top quark and a gluon. The search uses data collected with the CMS detector from pp collisions at a center-of-mass energy of √ s = 8 TeV, selecting events that have a single isolated muon or electron, an imbalance in transverse momentum, and at least six jets, of which one must be compatible with originating from the fragmentation of a b quark. The data, corresponding to an integrated luminosity of 19.5 fb −1 , show no significant excess over standard model predictions, and provide a lower limit of 803 GeV at 95% confidence on the mass of the spin-3/2 t * quark in an extension of the Randall-Sundrum model, assuming a 100% branching fraction of its decay into a top quark and a gluon. This is the first search for a spin-3/2 excited top quark performed at the LHC.
Measurements of the differential and double-differential Drell-Yan cross sections are presented u... more Measurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5 (4.8) fb−1 in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at $ \sqrt{s} $ = 7 TeV. The measured inclusive cross section in the Z-peak region (60–120 GeV) is σ(ℓℓ) = 986.4 ± 0.6 (stat.) ± 5.9 (exp. syst.) ± 21.7 (th. syst.) ± 21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections dσ/dm for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section d2σ/dm d|y| in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading o...
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