ABSTRACT A search for the rare decays \( {\text{B}}_{\text{s}}^0 \) → μ + μ − and B0 → μ + μ − is... more ABSTRACT A search for the rare decays \( {\text{B}}_{\text{s}}^0 \) → μ + μ − and B0 → μ + μ − is performed in pp collisions at \( \sqrt {s} = {7}\;{\text{TeV}} \) , with a data sample corresponding to an integrated luminosity of 5 fb−1 collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are \( \mathcal{B}\left( {{\text{B}}_{\text{s}}^0 \to {\mu^{ + }}{\mu^{ - }}} \right) < {7}.{7} \times {1}{0^{{ - {9}}}} \) and \( \mathcal{B}\left( {{{\text{B}}^0} \to {\mu^{ + }}{\mu^{ - }}} \right) < 1.8 \times {10^{{ - 9}}} \) at 95% confidence level.
Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limi... more Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limits on ZZγ and Zγγ triple gauge boson couplings The CMS Collaboration * Abstract A measurement of the Zγ → ννγ cross section in pp collisions at √ s = 7 TeV is presented, using data corresponding to an integrated luminosity of 5.0 fb −1 collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range |η| < 1.4 with transverse energy above 145 GeV. The Zγ → ννγ production cross section is measured to be 21.1 ± 4.2 (stat.) ± 4.3 (syst.) ± 0.5 (lum.) fb, which agrees with the standard model prediction of 21.9 ± 1.1 fb. The results are combined with the CMS measurement of Zγ production in the + − γ final state (where is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings: |h Z 3 | < 2.7 × 10 −3 , |h Z 4 | < 1.3 × 10 −5 for ZZγ and |h γ 3 | < 2.9 × 10 −3 , |h γ 4 | < 1.5 × 10 −5 for Zγγ couplings.
Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the... more Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at √ s N N = 5.02 TeV. Charged pions, kaons, and protons in the transverse-momentum range p T ≈ 0.1-1.7 GeV/c and laboratory rapidity |y| < 1 are identified via their energy loss in the silicon tracker. The average p T increases with particle mass and the charged multiplicity of the event. The increase of the average p T with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The p T spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity. C. Caillol, B. Clerbaux, G.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions w... more A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions with 35 pb −1 of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable R, related to the missing transverse energy E miss T . The new physics signal is characterized by a broad peak in the distribution of M R , an event-by-event indicator of the heavy particle mass scale. This new approach is complementary to E miss T -based searches. After background modeling based on data, and background rejection based on R and M R , no significant excess of events is found beyond the standard model expectations. The results are interpreted in the context of the constrained minimal supersymmetric standard model as well as two simplified supersymmetry models.
A sample of events enriched in bb̄ quark pairs was selected in the data recorded by the DELPHI ex... more A sample of events enriched in bb̄ quark pairs was selected in the data recorded by the DELPHI experiment at LEP during 1992 and 1993, by the presence of secondary decay vertices from short-lived particles. Using this sample, the average multiplicities of Ks0, K±, p(p̄), Λ(Λ) and of charged particles in bb̄ events have been measured, distinguishing the component from
Zeitschrift Fur Physik C-Particles and Fields, 1996
A search has been made for direct production of heavy quarkonium states in more than 3 million ha... more A search has been made for direct production of heavy quarkonium states in more than 3 million hadronic Z 0 decays in the 1991-1994 DELPHI data. Prompt J= , (2S) and candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay v ertex positions. New upper limits are set at the 90% condence level for Br(Z 0 Q Q X)=Br(Z 0 hadrons) for various strong production mechanisms of J= and ; these range down to 0:9 10 4 . The limits are set in the presence of a small excess ( 1% statistical probability of a background uctuation) in the sum of candidates from prompt J= , (2S), (1S); (2S) and (3S) relative to the estimated background.
Zeitschrift Fur Physik C-Particles and Fields, 1996
Reconstructed baryon decays and photon conversions in DELPHI are used to measure the 0 production... more Reconstructed baryon decays and photon conversions in DELPHI are used to measure the 0 production rate from hadronic Z 0 decays at LEP. The number of 0 decays per hadronic Z decay is found to be: < 0 + 0 >= 0 : 070 0:010 (stat:) 0:010 (syst:) :
Zeitschrift Fur Physik C-Particles and Fields, 1996
The average lifetime of b-baryons has been studied using 3 × 10 6 hadronic Z 0 decays collected b... more The average lifetime of b-baryons has been studied using 3 × 10 6 hadronic Z 0 decays collected by the DEL-PHI detector at LEP. Three methods have been used, based on the measurement of different observables: the proper decay time distribution of 206 vertices reconstructed with a Λ, a lepton and an oppositely charged pion; the impact parameter distribution of 441 muons with high transverse momentum accompanied by a Λ in the same jet; and the proper decay time distribution of 125 Λ c -lepton decay vertices with the Λ c exclusively reconstructed through its pKπ, pK 0 and Λ3π decay modes. The combined result is:
From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle m... more From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity o f w eakly decaying B hadrons was measured to be: 4:97 0:03 0:06 ; excluding the K 0 and decay products.
ABSTRACT A search for the rare decays \( {\text{B}}_{\text{s}}^0 \) → μ + μ − and B0 → μ + μ − is... more ABSTRACT A search for the rare decays \( {\text{B}}_{\text{s}}^0 \) → μ + μ − and B0 → μ + μ − is performed in pp collisions at \( \sqrt {s} = {7}\;{\text{TeV}} \) , with a data sample corresponding to an integrated luminosity of 5 fb−1 collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are \( \mathcal{B}\left( {{\text{B}}_{\text{s}}^0 \to {\mu^{ + }}{\mu^{ - }}} \right) &lt; {7}.{7} \times {1}{0^{{ - {9}}}} \) and \( \mathcal{B}\left( {{{\text{B}}^0} \to {\mu^{ + }}{\mu^{ - }}} \right) &lt; 1.8 \times {10^{{ - 9}}} \) at 95% confidence level.
Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limi... more Measurement of the production cross section for Zγ → ννγ in pp collisions at √ s = 7 TeV and limits on ZZγ and Zγγ triple gauge boson couplings The CMS Collaboration * Abstract A measurement of the Zγ → ννγ cross section in pp collisions at √ s = 7 TeV is presented, using data corresponding to an integrated luminosity of 5.0 fb −1 collected with the CMS detector. This measurement is based on the observation of events with an imbalance of transverse energy in excess of 130 GeV and a single photon in the absolute pseudorapidity range |η| < 1.4 with transverse energy above 145 GeV. The Zγ → ννγ production cross section is measured to be 21.1 ± 4.2 (stat.) ± 4.3 (syst.) ± 0.5 (lum.) fb, which agrees with the standard model prediction of 21.9 ± 1.1 fb. The results are combined with the CMS measurement of Zγ production in the + − γ final state (where is an electron or a muon) to yield the most stringent limits to date on triple gauge boson couplings: |h Z 3 | < 2.7 × 10 −3 , |h Z 4 | < 1.3 × 10 −5 for ZZγ and |h γ 3 | < 2.9 × 10 −3 , |h γ 4 | < 1.5 × 10 −5 for Zγγ couplings.
Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the... more Spectra of identified charged hadrons are measured in pPb collisions with the CMS detector at the LHC at √ s N N = 5.02 TeV. Charged pions, kaons, and protons in the transverse-momentum range p T ≈ 0.1-1.7 GeV/c and laboratory rapidity |y| < 1 are identified via their energy loss in the silicon tracker. The average p T increases with particle mass and the charged multiplicity of the event. The increase of the average p T with charged multiplicity is greater for heavier hadrons. Comparisons to Monte Carlo event generators reveal that Epos Lhc, which incorporates additional hydrodynamic evolution of the created system, is able to reproduce most of the data features, unlike Hijing and Ampt. The p T spectra and integrated yields are also compared to those measured in pp and PbPb collisions at various energies. The average transverse momentum and particle ratio measurements indicate that particle production at LHC energies is strongly correlated with event particle multiplicity. C. Caillol, B. Clerbaux, G.
Physical Review D - Particles, Fields, Gravitation and Cosmology, 2012
A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions w... more A search is performed for heavy particle pairs produced in √ s = 7 TeV proton-proton collisions with 35 pb −1 of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable R, related to the missing transverse energy E miss T . The new physics signal is characterized by a broad peak in the distribution of M R , an event-by-event indicator of the heavy particle mass scale. This new approach is complementary to E miss T -based searches. After background modeling based on data, and background rejection based on R and M R , no significant excess of events is found beyond the standard model expectations. The results are interpreted in the context of the constrained minimal supersymmetric standard model as well as two simplified supersymmetry models.
A sample of events enriched in bb̄ quark pairs was selected in the data recorded by the DELPHI ex... more A sample of events enriched in bb̄ quark pairs was selected in the data recorded by the DELPHI experiment at LEP during 1992 and 1993, by the presence of secondary decay vertices from short-lived particles. Using this sample, the average multiplicities of Ks0, K±, p(p̄), Λ(Λ) and of charged particles in bb̄ events have been measured, distinguishing the component from
Zeitschrift Fur Physik C-Particles and Fields, 1996
A search has been made for direct production of heavy quarkonium states in more than 3 million ha... more A search has been made for direct production of heavy quarkonium states in more than 3 million hadronic Z 0 decays in the 1991-1994 DELPHI data. Prompt J= , (2S) and candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay v ertex positions. New upper limits are set at the 90% condence level for Br(Z 0 Q Q X)=Br(Z 0 hadrons) for various strong production mechanisms of J= and ; these range down to 0:9 10 4 . The limits are set in the presence of a small excess ( 1% statistical probability of a background uctuation) in the sum of candidates from prompt J= , (2S), (1S); (2S) and (3S) relative to the estimated background.
Zeitschrift Fur Physik C-Particles and Fields, 1996
Reconstructed baryon decays and photon conversions in DELPHI are used to measure the 0 production... more Reconstructed baryon decays and photon conversions in DELPHI are used to measure the 0 production rate from hadronic Z 0 decays at LEP. The number of 0 decays per hadronic Z decay is found to be: < 0 + 0 >= 0 : 070 0:010 (stat:) 0:010 (syst:) :
Zeitschrift Fur Physik C-Particles and Fields, 1996
The average lifetime of b-baryons has been studied using 3 × 10 6 hadronic Z 0 decays collected b... more The average lifetime of b-baryons has been studied using 3 × 10 6 hadronic Z 0 decays collected by the DEL-PHI detector at LEP. Three methods have been used, based on the measurement of different observables: the proper decay time distribution of 206 vertices reconstructed with a Λ, a lepton and an oppositely charged pion; the impact parameter distribution of 441 muons with high transverse momentum accompanied by a Λ in the same jet; and the proper decay time distribution of 125 Λ c -lepton decay vertices with the Λ c exclusively reconstructed through its pKπ, pK 0 and Λ3π decay modes. The combined result is:
From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle m... more From the Z decays recorded in 1994 and 1995 by the DELPHI detector at LEP, the charged particle multiplicity o f w eakly decaying B hadrons was measured to be: 4:97 0:03 0:06 ; excluding the K 0 and decay products.
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Papers by T. Rovelli