The Compact Muon Solenoid Experiment. Conference Report. Mailing address: CMS CERN, CH-1211 GENEVA 23, Switzerland

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1 Available on CMS information server CMS CR -08/036 he Compact Muon Solenoid Experiment Conference Report Mailing address: CMS CERN, CH GENEVA 3, Switzerland 30 April 08 (v4, 08 May 08) Measurement of the BEH scalar mass and other couplings in ALAS and CMS David Sperka for the ALAS, CMS and Higgs collaborations. Abstract he CMS and ALAS collaborations have performed numerous studies of the Higgs boson s properties using pp collisions from the LHC at s = 3 ev during 06. hese studies include precision measurements of the Higgs boson s mass, which is a free parameter of the Standard Model. he Higgs bosons couplings have been constrained by combining the measurements of multiple production and decay channels. hese measurements can also be used to place indirect constraints on physics beyond the standard model involving extended Higgs sectors. Presented at Moriond/EW08 53rd Rencontres de Moriond 08 Electroweak Interactions and Unified heories

2 Measurements of the BEH scalar mass and other couplings in ALAS and CMS David Sperka University of Florida, Gainesville, Florida (On behalf of the ALAS and CMS collaborations) he ALAS and CMS collaborations have performed numerous studies of the Higgs boson s properties using pp collisions from the LHC at s = 3 ev during 06. hese studies include precision measurements of the Higgs boson s mass, which is a free parameter of the Standard Model. he Higgs boson s couplings have been constrained by combining the measurements of multiple production and decay channels. hese measurements can also be used to place indirect constraints on physics beyond the standard model involving extended Higgs sectors. Introduction After the discovery of a Higgs boson with a mass of around 5 GeV by the ALAS and CMS collaborations, a large part of the future of the Higgs physics program at the LHC will consist of precision measurements of its couplings to Standard Model () particles. heories beyond the (B) predict modifications to these couplings which can vary between 0.% %, depending on the parameters of different models. As will be shown, current measurements already probe O(%) modifications, and the High Luminosity LHC will be able to probe O(%) modifications. An important prerequisite for this program is a precision measurement of the Higgs boson mass, since an O(0 MeV) uncertainty in can also lead to O(%) modifications to the Higgs couplings. he Higgs boson mass is also an interesting measurement in its own right, since it is not predicted by the and plays an important role in understanding the hierarchy problem as well as the Electroweak vacuum structure and the stability of the universe. During 06, the ALAS and CMS experiments both recorded datasets corresponding to about 36 fb of pp collisions at a center of mass energy of s =3 ev. hese datasets have been used to improve the precision on the measurement of the Higgs boson mass and couplings, and chart the course for the future of Higgs physics at the LHC. Measurements of the Higgs boson s mass he H γγ and H ZZ 4l decay modes have the best mass resolution and are therefore used to measure the Higgs boson mass. he preliminary measurement from ALAS 3 combines both

3 decay channels, while the published result from CMS uses only the H ZZ 4l decay mode 4. he ALAS analysis of the H γγ decay channel divides events into categories with different mass resolution and signal to background ratio. he signal is then fit as a peak above the continuum diphoton background. he main systematic uncertainties in the measurement come from the determination of the photon energy scale, including the LAr cell non-linearity, interlayer calibration, and material description. For the analysis of the H ZZ 4l decay channel, both CMS and ALAS use a similar strategy. A multivariate discriminator is used to better separate signal events from background events. A kinematic fit of two of the leptons is performed to constrain their invariant mass to the known Z-boson mass, improving the mass resolution. he uncertainty in the 4l mass is determined event-by-event, improving both the accuracy and precision of the measurement. he main systematic uncertainty is the determination of the lepton energy and momentum scales. he result of the ALAS measurement is = 4.98 ± 0.6 (±0.9 stat. ± 0. sys.) GeV and is shown in the top panel of Figure. he H γγ decay channel is dominated by the systematic uncertainties and the H ZZ 4l decay channel is dominated by the statistical uncertainties. he result of the CMS measurement in the H ZZ 4l decay channel is = 5.6 ± 0. (±0.0 stat. ± 0.08 sys.) GeV and is shown in the bottom panel of Figure. his is currently the single most precise determination of the Higgs boson mass, surpassing the precision of the combined ALAS and CMS measurement using Run data, where the result was = 5.09 ± 0.4 (±0. stat. ± 0. sys.) GeV. ALAS Preliminary s = 3 ev, 36. fb otal Stat. Syst. otal Stat. Syst. LHC Run 5.09 ± 0.4 ( ± 0. ± 0.) GeV H ZZ* 4l 4.88 ± 0.37 ( ± 0.37 ± 0.05) GeV H γ γ 5. ± 0.4 ( ± 0. ± 0.36) GeV Combined 4.98 ± 0.8 ( ± 0.9 ± 0.) GeV [GeV] Events / GeV CMS H(5) qq ZZ, Zγ* gg ZZ, Zγ* Z+X (3 ev) - lnl CMS 4 e 4e Combined Combined (stat. only) (3 ev) m 4l (GeV) (GeV) Figure op: Summary of the Higgs mass measurements in ALAS and a comparison with the ALAS and CMS combination using Run data 3. Bottom: Reconstructed 4l mass distribution in CMS and the likelihood value in each final state and their combination as a function of 4. 3 Measurements using the WW decay channel in CMS Given the precise measurement of, the next step is to measure the Higgs boson s couplings. he analysis of the H WW decay mode is an extremely important channel in this program,

4 given its large branching fraction and relatively low background rates. his channel is sensitive to almost all Higgs boson production mechanisms. For Moriond Electroweak, CMS has released an analysis of the WW decay channel using the full 06 dataset 5. he analysis begins by categorizing events based on the number of leptons and number of associated jets. he events are further split based on the lepton flavor and charge composition to create categories with different signal to background ratios. Events with associated jets are also categorized based on the dijet invariant mass and pseudorapidity difference to create categories sensitive to VBF and VH production. his categorization results in a total of 30 signal regions sensitive to ggh, VBF, WH and ZH production. Dedicated control regions for the dominant tt, Z ll, and VV backgrounds are fit together with the signal regions to constrain the background rates. he signal is extracted using binned templates of different sensitive observables depending on the category. he combined signal strength is measured to be = =.8 ± 0. (stat.) ± 0. (sys.) (theo.). he main theoretical uncertainties are ggh cross section and jet bin migration, and the main experimental systematics come from the background rates, luminosity measurement, and lepton identification efficiencies. he signal strengths as a function of the analysis category and production mode are shown in Figure. It should also be noted that the ALAS collaboration also released an analysis of the H WW decay channel for Moriond Electroweak 6. 0 jet DF ggh tagged +0.4 = jet DF ggh tagged +0.3 = jet DF ggh tagged = jet SF ggh tagged +0.6 = jet SF ggh tagged = jet VBF tagged = jet VH tagged +.3 = lepton WH tagged +.76 = lepton ZH tagged +.49 = (3 ev) H WW Combination +0.8 =.8 comb 0.7 ggh VBF WH ZH =.38 = 0.9 = 3.7 = (3 ev) Combination +0.8 =.8 comb 0.7 H WW σ/σ (a) σ/σ (b) Figure Left: Measured signal strengths in the CMS H WW analysis as a function of the analysis category. Right: Measured signal strengths per Higgs production mechanism 5. 4 Combined Higgs measurements Once the individual analyses of different Higgs decay channels are finished, the next step is to produce combined global fits to extract the Higgs couplings. his is necessary because different usually different couplings are involved in the production and decay, and often a single analysis is unable to resolve the ambiguity. he ALAS collaboration has performed a preliminary combination of the H ZZ 4l and H γγ decay channels 7. hese results include model independent measurements of the Higgs production in a simplified fiducial volume y(h) <.5. In these measurements the theoretical uncertainties in the inclusive predictions are separated from experimental and theoretical uncertainties affecting the measurements. his is done for both the conventional production modes, as well as (for the first time) for a more granular approach where ggh and VBF production are further broken down into different kinematic regions, shown in the top panel of Figure 3. Also included in these results are constraints on Higgs couplings. he bottom panel of Figure 3 shows the -dimensional confidence s obtained for parameterizations assuming different coupling modifiers for fermions and vector

5 bosons, or for the loop-induced ggh and H γγ processes. [pb] / B 4l B 4l gg H, 0-jet gg H, -jet ph < 60 GeV ALAS preliminary s = 3 ev, 36. fb H γ γ and H ZZ* 4l = 5.09 GeV, y <.5 H qq Hqq j p < 00 GeV σ i κ f / B 4l i B γ γ prediction Best fit Combined 68% CL Combined 95% CL H γγ 68% CL H ZZ* 4l 68% CL gg H, -jet 60 ph < 0 GeV gg H, -jet 0 ph < 00 GeV κ V gg H, -jet ph < 00 GeV or VBF-like gg H, -jet ph 00 GeV + qq Hqq j p 00 GeV Simplified template cross section measurements ALAS Preliminary s = 3 ev, 36. fb H γ γ and H ZZ* 4l = 5.09 GeV κ γ prediction Best fit 68% CL 95% CL gg/qq Hll/Hlν gg/qq tth ALAS Preliminary s = 3 ev, 36. fb H γ γ and H ZZ* 4l = 5.09 GeV κ g Figure 3 Combined Higgs measurements in ALAS 7. he top panel shows the simplified fiducial cross section in different kinematic regions. he bottom panel shows the -dimensional confidence s obtained for parameterizations assuming different coupling modifiers for fermions and vector bosons, or for the loop-induced ggh and H γγ processes. For Moriond Electroweak, CMS has released a preliminary combination of the measurements based on the 06 dataset 8. he combination includes a wide range of measurements and is sensitive to out of 5 possible production decay combinations, considering the major production and decay channels. Figure 4 shows the combined signal strengths as a function of the production and decay mode, as well as measurements in the simplified fiducial volume y(h) <.5 for the conventional Higgs production mechanisms. he signal strengths per production mode result in significant improvements in the precision of the measurements of ggh and tth by 33% and 50%, respectively, compared to the previous ALAS and CMS combination using the Run dataset. ggh VBF WH ZH tth (3 ev) ±σ (stat. sys.) ±σ (sys.) ±σ γ γ ZZ WW ττ bb (3 ev) ±σ (stat. sys.) ±σ (sys.) ±σ ZZ (pb) / BR ZZ x BR σ i ZZ / BR BR gg H VBF H+V(qq) H+W(lν) Stage 0 Simplified emplate Cross Sections y <.5 H bb WW ττ H+Z(ll/νν) ±σ (stat. sys.) ±σ (stat. sys.) ±σ (sys.) prediction γγ (3 ev) tth+th Figure 4 Combined Higgs measurements in CMS 8 showing the signal strength per production mechanism (left) and decay channel (middle). Also shown are the measurements in the simplified fiducial volume y(h) <.5 for the conventional Higgs production mechanisms (right). he combined results from CMS also include interpretations in terms of Higgs couplings under different assumptions. he left panel of Figure 5 shows the measured couplings assuming the structure of the ggh and H γγ processes, as well as their scaling as a function of the

6 particle mass. he middle panel of Figure 5 shows the measured couplings without assuming the structure of the loop induced processes but assuming no B contribution to the total Higgs width, and finally the right panel allows for B contributions to the total Higgs width but assumes κ V <. In all cases, the results are compatible with the predictions. Constraints are therefore derived on B branching fractions to invisible particles (BR inv. <0.) and undetected final states (BR undet. <0.9) at 95% confidence level. m v V κ V or m v F κ F Ratio to τ b (3 ev) t W Z Higgs boson [M, ε] fit ± σ ± σ 0 Particle mass [GeV] κ Z κ W κ t κ τ κ b κ g κ γ (3 ev) σ σ κ Z κ W κ t κ τ κ b κ g κ γ B inv B undet. (3 ev) σ σ Figure 5 Combined measurements of Higgs couplings in CMS 8. he left panel assumes the structure of loop processes. he middle panel allows for B contributions to loop processes but no B contributions to the total Higgs width. he right panel allows for B contributions to loop processes and the total Higgs width, but assumes κ V <. Finally, the combined CMS measurement provides constraints on extended Higgs sectors. In order to not spoil electroweak symmetry breaking, the couplings of the 5 GeV Higgs boson will be modified in any B model with an extended Higgs sector. Figure 6 shows the constraints in the -dimensional parameter space tanβ vs. cos(β α) of different benchmark wo Higgs Doublet models: ype I (left), ype II (middle), and the hms 9 (right). tanβ (3 ev) tanβ (3 ev) tanβ (3 ev) hms 95% CL Expected 95% CL HDM ype I HDM ype II 95% CL 95% CL Expected 95% CL Expected 95% CL cos(β-α) cos(β-α) m A (GeV) Figure 6 Constraints from CMS 8 in the -dimensional parameter space tanβ vs. cos(β α) of different benchmark wo Higgs Doublet models: ype I (left), ype II (middle), and the hms (right). 5 Constraints on light quark Yukawa couplings in ALAS he aforementioned results provide constraints on the most significant Higgs couplings, namely to vector bosons and third generation fermions. It is natural to wonder whether the couplings of the Higgs boson to first and second generation fermions can be constrained. In the lepton sector this is accomplished by searching for the decay H, while the quark sector is more challenging. he ALAS collaboration has published the first search for the rare Higgs decays H φγ and H ργ which can constrain the Higgs boson s couplings to second and first generation quarks, respectively. he analysis searches for a peak in the K + K γ or π + π γ

7 invariant mass distributions, which are shown in Figure 7. In the absence of a signal, limits are set on the rare branching ratios H φγ and H ργ respectively at 08 times and 5 times the predictions. Events / GeV ALAS s=3 ev, 35.6 fb Events / GeV ALAS s=3 ev, 3.3 fb Background Fit ±σ 400 Background Fit ±σ 50 Background 4 B(H φγ)=4.8 6 B(Z φγ)= Background 4 B(H ργ)=8.8 6 B(Z ργ)=5 / Fit [GeV] + m K K γ / Fit m π + π [GeV] γ Figure 7 he reconstructed K + K γ (left) and π + π γ (right) invariant mass distributions from the ALAS search for H φγ and H ργ. 6 Conclusions he CMS and ALAS collaborations both had extremely fruitful physics runs during 06, performing numerous studies of the Higgs boson s properties using pp collisions from the LHC at s = 3 ev. hese studies include precision measurements of the Higgs boson s mass, and the Higgs boson s couplings have been constrained by combining the measurements of multiple production and decay channels. he precision of the measurements has surpassed those from Run for key observables, including ggh and tth production. hese measurements have also be used to place indirect constraints on physics beyond the standard model involving extended Higgs sectors. With more data, ALAS and CMS should be able to see the deviations predicted by many B models. References. ALAS Collaboration, JINS 3 S08003 (008).. CMS Collaboration, JINS 3 S08004 (008). 3. ALAS Collaboration, ALAS-CONF , 4. CMS Collaboration, JHEP(07) CMS Collaboration, CMS-PAS-HIG6-04, 6. ALAS Collaboration, ALAS-CONF , 7. ALAS Collaboration, ALAS-CONF , 8. CMS Collaboration, CMS-PAS-HIG7-03, 9. A. Djouadi et. al., Eur. Phys. J. C 73 (03) 650. ALAS Collaboration, arxiv: