Photon decay modes of the intermediate mass Higgs ECFA Higgs workmg group C.Seez and T. Virdee L. DiLella, R. Kleiss, Z. Kunszt and W. J .Stirlin g
Presented at the LHC Workshop, Aachen, 4 - 9 October 1990 by C. Seez, Imperial College, London.
A report is given of studies of: (a) H —> yy (work done by C. Seez and T. Virdee) (b) W H -> yy (work done by L. DiLella, R. Kleiss, Z. Kunszt and W. J. Stirling) for Higgs bosons in the intermediate mass range (90< mH Introduction A Standard Model neutral Higgs boson having a mass above the highest reach of LEP II (around 90 GeV/cz) [1], and below about 2mZ will be difficult to detect at a hadron collider. The most promising channels for detection are H0- >yy, or, for muzi 30 GeV/c2, H0->ZZ*->e+e·e+e· [2]. As the decay width of the Higgs is about 5.5 MeV at mH=100 GeV/c2, and 8.3 MeV at 150 GeV/c2, the width of the reconstructed mass distribution, and hence the signal/background ratio, will be limited by the detector, and in particular by the energy resolution of the electromagnetic calorimeter. The decay channel H9 —> Zy also appears to be potentially attractive, but, after requiring that the Z decay into electrons or muons, the combined branching fraction times cross·section is very small. The intrinsic background (i.e. the background with the same final state as the signal) is large and rules out the possibility of detecting the Higgs boson in this channel. In this paper a detailed study of the possibility of detecting an intermediate mass Higgs boson in the di-photon channel is reported. Results from another study are also reported in which the same decay is considered but for a Higgs boson produced in association with an intermediate vector boson. 1. H0 -> Previous studies of H9 -> yy [3] concluded that it would probably be possible to fmd a Higgs of mass 150 GeV/cz at the SSC (\}s=40 TeV, and 104/pb) with an excellent calorimeter, but that it would probably not be possible to obtain a significant signal if the mass was 100 GeV/c2. The study described here differs from this previous work by: a) considering LHC energies and luminosities (\}s=l6TeV, and 105/pb) and the problems resulting from pileup, b) investigating a large range of calorimetric energy resolutions, c) including the prompt photon background from bremsstrahlung diagrams, and d) making a detailed study of the background from jet processes. 2. Cross-sections The Higgs production cross-section multiplied by the branching ratio to two photons (c$H.Brw) has recently been re-calculated by Kunszt and Stirling [4] for Higgs masses in the 474 OCR Output 475 intermediate range, and is shown in figure l. The background to the H0->*yy signal may be divided into three categories: i) prompt di-photon production from the quark annihilation and box diagrams which provides an intrinsic background, ii) prompt di-photon production from significant higher order diagrams (mainly bremsstrahlun g diagrams), iii) the background from jet processes where an electromagnetic energy deposit results from a quark or gluon jet rather than a prompt photon. The intrinsic background cross—sections have been calculated using ISAJET [5] as a framework with the matrix elements of Berger, Braaten and Field [6]. For this calculation the HMRSB structure functions [7] were inserted into ISAJET so as to be consistent with the calculation of the Higgs production cross-section. The bremsstrahlung contribution can be generated with ISA] ET. Its cross-section has been fixed by requiring the ratio bremsstrahlung/(quark annihilation+box diagrams) to be that calculated by the direct photon working group [8]. The calculated cross-section for Higgs boson production in the intermediate mass range is insensitive to the choice of top quark mass: for mH=l0O GeV/cz it varies by less than 10% for values of top mass ranging from 100 to 200 GeV/c2. However, choice of structure functions can vary the calculated cross-sections for both Higgs production and the background processes by i50%, even when the choice is restricted to sets fitting recent BCDMS data [9]. Tables 1 and 2 summarise the cross—sections used. For both signal and background processes Monte-Carlo events have been generated using ISAJ ET. mg (GeV/c2) 0.Br (H0—>vy) (fb) before cuts after cuts 80 36.4 9.6 100 46.5 19.0 150 26.5 13.5 Z. Kunszt and W. J. Stirling, HMRSB structure functions, m,0p=150 GeV/cz kinematic cuts: h]|£2, pTl>40, pT2>25GeV/c, pTl/(pTl+pT2)<0.7 Table I : The cross—sccti0n 0f the signal OCR Output 476 mw qq—>·Yy gg—>Yy Brems- Total (GeV/c2) strahlung 80 31.7 84.7 87.5 204. 100 30.8 60.8 61.4 153. 150 12.0 16.1 17.0 45. do/dmw (fb/GeV) of di-photon backgrounds kinematic cuts: |n|S2, pT1>40, pT2>25GeV/c, pTl/(pT1+pT2)<0.7 qq->yy, gg->*y;a ISA] ET, using matrix elements of Berger, Braaten and Field, HMRSB structure functions Bremsstrahlung: ISAJET, after isolation cut, normalized to analytic calculation (see text) £1b!Q.·I@ crpas-sections ofthe prompt di-photon backgrounds 3. The calorimeter, acceptance and cuts If quantitative and realistic results are to be produced it is necessary to define the properties and characteristics of a detector whose performance can then be simulated. The model calorimeter used in this study covers a pseudo—rapidity range -2 S 1] S 2, and has an inner radius of 2 metres at 1]:0, tapering to 1.5 metres at 1]:12. It is segmented into fully pointing towers, and it is assumed that sufficient lateral shower containment is obtained by reading out an area of 20 x 20 cm2, i.e. photons are reconstructed in an area of A¢xAn=0.1x0.1. It is assumed that only the energy deposited by the interactions occuring in a single bunch crossing is seen. The cuts placed on the photon transverse momenta are sufficiently high that triggering would pose no problem: pTl > 40 and py? > 25 GeV/c (the photons being ordered by Pr) The photon pairs from bremsstrahlung diagrams tend to be asymmetric in the amount of transverse momentum they carry. A cut on the pT balance of the photon pair, pTl/(pTl+pT2)<0.7 (where pTl>p-Y2), is found to remove about 20% of the bremsstrahlung background remaining after the 11 and PT cuts at mflllo GeV/c2 while removing only 6.2% of the signal. Since this cut rejects very little of the background contributions from the annihilation and box diagrams the gain in signal significance (measured by NS/VNS) is, unfortunately, small. As is described below, an isolation cut is applied to the photons to help reject the jet background. This isolation cut, though only over a small area (AnxA¢=0.1x0.1), should significantly reduce the remaining hard bremsstrahlung even after the application of the balance cut, as is shown by a semi-analytic calculation [8]. However, the algorithm used in ISAJET to generate photon radiation from quarks during their 'evo1ution' results in a distribution of the radial separation between radiating quark and photon that is essentially flat, rather than being strongly peaked around AR=0. Consequently the isolation cut has little effect on the OCR Output bremsstrahlung events generated with ISAJET. We assume that this is incorrect and have corrected the level of the bremsstrahlung background assuming that our isolation cut over an area of AnxA¢=0.2x0.2, after the PT balance cut, should further reduce it by 50%, as is suggested by the analytic calculation. The cuts against the bremsstrahlun g background could be further optimised. A fairly loose cut on the EET within a somewhat larger isolation area about the photons, e.g. a circle of radius AR=0.3, should be very effective in reducing the bremsstrahlung background. Since the photons failing the balance cut are, in general, accompanied by harder jets than those passing it, an efficient isolation cut should make the py balance cut unnecessary. This deserves to be studied with a realistic simulation taking account of the energy deposited in the isolation cone by pileup. The limited rapidity range results in a geometric acceptance of around one half (47.1% at mH=80 GeV/c2, 48.2% at mH=10O GeV/02, and 52.6% at mH=150 GeV/cz). Figure 2 shows the distribution of the absolute rapidity of the photon, in each event, at the highest absolute rapidity, for photon pairs from (a) a Higgs of mass 100 GeV/cz, (b) the two prompt di-photon background diagrams. In all cases a requirement of pTl>40 and pT2>25 GeV/c has been made on the photons. For the background processes a mass cut of 105 2 mw2 95 GeV/c2 has also been made. The cuts on the transverse momenta of the photons result in very little additional loss of the signal for mH>100 GeV/cz and thus the final acceptance is 40.9% for mH=100 GeV/cz, and 50.8% for mH=l50 GeV/c2. At mH=80 GeV/c2 the transverse momentum cuts significantly deplete the signal (the final acceptance is 26.4%), however, because the pq- spectra of the intrinsic background is so steep at low pT, reducing the pT cuts gives only a small gain in the ratio signal/N/background. Figure 3 shows the pq- distribution of photons from (a) a Higgs of mass 100 GeV/c2, (b) qq -> yy with 105 2 mw 2 95 GeV/c2, and (c) gg -> yy with 105 2 m,,,2 95 GeV/c2. In all cases a requirement of -2 Sn S 2 has been made on the photons. The significance of the signal could be somewhat improved by extending the coverage of the calorimeter to larger rapdities. For example, for Higgs of mass 100 GeV/cz, increasing the coverage from -2 S n S 2, to -3 Sn S 3 increases the acceptance, after py cuts, by 45%. The background, however, is increased by more than 50%. This results in a gain in the signal significance of about 18%. Despite many references in the literature to further cuts which enhance the signal with respect to the intrinsic di-photon background we have found no cut which usefully improves the significance of the signal. The cut on large values of lcos0“”I (the photon scattering angle in the centre-of-mass frame of the two photons) originally advocated by Dicus and Willenbrock [10] (for computational reasons in the absence of n and pT cuts) and used in most subsequent studies has no power at all after the n and pT cuts have been applied. 4. Multiple interactions Taking a mean operating luminosity of 1034 cm·2sec·l and an inelastic non-single diffractive p-p cross-section of 60mb, one obtains a mean interaction rate of 600 MHz — an average of 9 477 OCR Output interactions each crossing for a l5ns bunch spacing. These multiple interactions have a number of effects upon the detection of Higgs di·photon decays. 4.1 energy smearing Energy may be deposited into the calorimeter cells used to measure a photon's energy from any of the interactions which occur during the cells' effective integration time. This pileup energy smears the signal, and the magnitude of the effect depends upon the size of the area of the calorimeter needed to laterally contain the shower (in our case At’pxAn=0.1x0.1), the effective integration time (in our case a single bunch crossing), and upon the instantaneous luminosity. The magnitude of this effect has been estimated by Monte—Carlo. Jet events were generated using ISAJET with the jet pT>5 GeV/c. These events were assumed to represent the events accompanying a di-photon trigger. Pileup was then simulated by overlaying a number of these events, the number overlayed being chosen from a Poisson distribution with a mean of 10. All particles were assumed to deposit all their energy in the electromagnetic calorimeter. Figure 4(c) shows the smearing of mass resolution resulting from this pileup alone (i.e. the energy resolution is taken to be otherwise perfect). The broadening of the effective mass peak shown in figure 4(c) may be compared to that caused by a calorimetric resolution of 2%/JE G9 0.5% (where G3 denotes a quadratic sum) as shown in figure 4(a). lt can be seen that the pileup smearing is relatively insignificant. 4.2 signal rejection As will be discussed below it is necessary to impose an isolation requirement on electromagnetic clusters found in the calorimeter to help reduce the number of such clusters resulting from jet processes. The multiple piled up events increase the probability that the photons from the Higgs decay fail the isolation criteria. Isolation requirements are discussed in more detail below. 4.3 loss of knowledge of the vertex position Although the transverse location of interactions in an LHC experiment will be known with great precision, the longitudinal position of the interactions will, because of the length of the bunches, be distributed with an r.m.s. spread of 5-6 cm. If it is not known to which vertex the photons belong the recontructed mass is smeared by the resulting uncertainty on the angle between the photons. The effect on the width of the reconstructed effective mass for a Higgs of mass 100 GeV/c2 is shown in figure 4(d), where it can be seen that the broadening of the mass peak is of similar magnitude to that resulting from a calorimetric resolution of 7 %/VE G3 1.0% shown in figure 4 (b). With our chosen geometry a knowledge of the longitudinal vertex position to a precision of about l cm results in a smearing of the reconstructed effective mass which is small compared to that caused by even an superb calorimeter. It may be possible, by measuring the shower position at two depths, to obtain the necessary angular information from the photon showers themselves. Some results are shown below for the case where such a capability is assumed to exist. 478 OCR Output A charged particle tracking device will find many vertices per crossing, and it will sometimes be possible to determine which vertex corresponds to the interaction in which the Higgs was produced, by, for example, counting the number of high PT tracks associated with each vertex. This has been studied by Monte-Carlo. It does not seem possible to make the determination with sufficient efficiency for it to be very useful when there are on average 10 interactions per bunch crossing. 5. The jet background In the kinematic region being considered the di-jet cross-section is about seven orders of magnitude larger than the di-photon cross·section. A very large rejection of the possibility of any di-jet event faking a di-photon event is needed if the jets are not to be the source of a formidable background. Two tools can be used to reject the jet background: Isolation: the photons from Higgs decay are isolated whereas the electromagnetic energy deposits resulting from a jet tend to be accompanied by other jet fragments. Isolation has traditionally been imposed at hadron colliders by cutting on the summed transverse energy within a relatively large cone around the particle to be isolated. Because of the large average EET deposited into any such cone from the many interactions occuring every bunch crossing at high luminosity such a cut cannot be made very tight. For example: if the mean number of interactions per bunch crossing is 10, then the r.m.s. fluctuation on the EET deposited in a cone of AR=0.6 by the pileup events in a single bunch crossing is about 5 GeV, thus the cut would have to be set at 10 GeV, or more, to avoid the rejection of a significant fraction of the signal (the mean EET in such a cone is about l2 GeV, but this can be considered to be merely a shift of the zero·point). A useful rejection factor can be obtained by cutting on relatively small individual energy deposits (or tracks) in a small region around the candidate isolated photons. It is clear that the precise definition of the isolation criteria need to be optimised with a full shower Monte-Carlo for any given detector design. For the results presented here the threshold was taken to be p>2GeV/cz, and the isolation region was taken to be a square 40x40 cm2 (i.e. Aq>xA1]=0.2x0.2). 1:0 detection: the jet background is predominantly due to single TlZ0'S carrying a large fraction of the jet ET, the decay photons of which are reconstmcted as a single electromagnetic energy deposit. The ability to acertain, with a position detector for example, that there are two photons and not one in an electromagnetic energy deposit is thus a powerful tool to reject the jet background. With the geometry assumed in this study the minimum separation of the photons from the decay of a no with pT=20G€V/ c2 is 2.7 cm. It has been assumed that a position detector is present that can reliably detect the presence of two showers when they are separated by more than lcm. To avoid prohibitive demands on computer time it is necessary to investigate the rejection of single jets, and from this calculate the rejection factor against di-jets. The uncertainty about the level of the background from jets is large, and arises from the following sources: lack of knowledge of the jet cross-section x3 OCR Output 480 lack of knowledge of the hard tail of the fragmentation functions x22 inadequacy of the simulation (not full shower simulation), and choice of isolation and no detection algorithms x22 The second and third items listed above refer to uncertainties on the single jet rejection factor and so enter the di—jet uncertainty squared. Adding these uncertainties quadratically gives a value larger than 5. LEP data allows a check of the quark fragmentation function in the energy range of interest, and the statistical precision in the hard tail will increase over the next few years. A detailed calorimeter design would allow a fuller simulation of the isolation and no detection. Nevertheless it seems clear that the uncertainty on the Monte-Carlo calculation of the jet background will always remain large. lt is necessary, therefore, to aim for a large safety margin in rejection power against the jet background. In practice this sets the goal of reducing the jet background to a level well below that of the intrinsic two photon background. ISAJET (with EHLQ structure functions) was used to generate 100000 jet events in each of 12 bins in pTh¤*d (l5$pT*¤¤*d$200 GeV/c). The results of the first stage of the investigation are plotted in figure 5. It shows the inclusive cross—sections, as a function of pq-, of jets, nos, isolated nos, and electromagnetic energy deposits originating from nos and not rejected by any Cuts. Also shown are the cross-sections of the direct di-photon processes mentioned above. All the cross-sections are shown after a cut of -2$r]$2 has been applied. The number of ys originating from nos and not rejected by any cuts has been obtained by decaying each isolated no 10 times and finding the resulting separation of the photons in the detector. At low pT the minimum separation of decay ys is greater than 1 cm, so it is the asymmetric decays where the separation is such that the lower energy photon falls outside the 40x40 cm isolation boundary which result in the background from unidentified nos. At higher PT the minimum separation of decay Ys becomes less than 1 cm and the position detector loses its HU rejection power. It can be seen that for pT>25 GeV/c the spectrum of the remaining ·ys is lower than halfway between the jet and the direct di—photon spectra (on the logarithmic scale), suggesting that when the rejection is applied to both jets the di-photon spectrum from di-jet events is below the direct di-photon spectrum. To obtain a quantative estimate of this background cross-section the two-dimensional distribution of the p-F of the two jets in each of a series of jet-jet mass bins was obtained, together with the jet cross-section in that bin. The rejection factors as a function of pT were then applied to obtain the jet background cross-section as a function of mass, which is plotted in iigure 6. It can be seen that only after using the no rejection power of the position detector is the background reduced to an insignificant level as compared to the prompt di-photon background. 6. Results Table 3 shows a summary of the results obtained, for three Higgs masses, assuming the presence of a superb electromagnetic calorimeter. For each mass the table shows the optimum mass bin width, Am, and the number of signal, Ns, and the number of background events, NB, counted in a bin of that width for an integrated luminosity of 105 /pb. The last column of the OCR Output table shows the significance of the signal seen. The simulations used to obtain the numbers in the table were made with the following conditions: The kinematic cuts described previously were applied: |n|$2, pq-1>40, p·l·2>25GeV/c, ml/ crossing. A 90% reconstruction efficiency on each photon (i.e. a further 19% loss of both signal and background) was assumed. It was assumed that the jet background had been reduced to negligible levels (position detector needed). It can be seen that, by using such an electromagnetic calorimeter, a highly significant signal can be seen at mH=l00 GeV/c2 and mH=150 GeV/c2. For Higgs bosons with masses between these two values the situation is even more favorable. However the significance drops away fairly rapidly for Higgs masses below 100 GeV/cz mn (GeV/c2) Am N S NB NS N NB 80 1.0 560 15400 4.5 100 1.5 1110 17300 8.4 150 2.0 880 6800 10.7 Table 3: Sizniziccmce 0fH0->wsi2nal at different masses Figure 7 presents the results in a slightly different form. A resolution function of the form AE/E=a/JE EB b, where the two terms are added quadratically, is assumed for the electromagnetic calorimeter. The significance of the signal seen from a Higgs boson of mass 100 GeV/cz, after accumulating 105 /pb of data, is plotted as a function of the sampling term, a. It is again assumed that the jet background had been reduced to negligible levels. The 4 lines show the effect on the significance of the mass resolution resulting from: the calorimeter resolution alone, the calorimeter resolution and the pileup (from a mean of 10 events per crossing as described above), the calorimeter resolution, pileup and a longitudinal vertex resolution of 1 cm, the calorimeter resolution, pileup and a longitudinal vertex resolution of 5.5 cm. 481 OCR Output In figure7(a) the constant term, b, is taken to be 0.5%, in figure 7(b) it is taken to be 1.0%. These plots emphasise the importance of the constant term, b, and the need for a means to locate the Higgs vertex in order to be able to exploit the power of a calorimeter with such a small sampling term. 7. W H0 -> e(tt)’yy The two photon decay mode was also considered for the special case where the Higgs boson is produced in association with an intermediate vector boson which decays leptonically. In these events the presence of a high PT isolated lepton in the final state provides an additional means of supressing the hadronic backgrounds. Table 4 shows the expected number of yy pairs, found in the mass windows specified in the table, resulting from the decay of a Higgs boson and accompanied by an isolated electron or muon from a W. The numbers given assume an integrated luminosity of 105 /pb, a rapidity coverage of t2.5 and a pq- threshold of 20 GeV/c for both the photons and lepton, with an efficiency of 85% for each y and 90% for the lepton after isolation cuts. The fraction of the signal falling in the chosen mass windows (about 80%) is taken to be the same as calculated by the simulation of unaccompanied H->yy detected by a high resolution calorimeter as described in section 6. In fact, the presence of a charged track, enabling the precise determination of the longitudinal vertex position, might allow a slightly better mass resolution to be achieved. The rate for Higgs produced in association with Zos is about 6 times lower and thus this channel cannot be considered viable for an integrated luminosity of 105 /pb. The background contributions from the following processes were evaluated: W+yy, the intrinsic or "irreducible" background [l 1] bE+yy, where one b-quark decays leptonically b5+y, where one b-quark decays leptonically, and the other fakes a photon W+2jets, where the jets fake photons bB+gluon, where one b-quark decays leptonically and both the other b-quark and the gluon fake photons. m Signal Am Backgrounds (GeV7c2) _(GeV/c2) Wyy bbyy g W+2jets 80 14.6 1.0 1.8 0.29 0.44 0.20 0.05 100 17.8 1.5 1.7 0.38 0.28 0.18 0.05 140 10.8 2.0 1.4 0.30 0.22 0.17 0.09 Table 4: W H0-> egtgjggsignal and backgrounds for 105_[pp_ The study was done at the parton level. It was assumed that a lepton isolation cut gives a factor of 7 rejection against leptons originating from b-quarks. The estimated background 482 OCR Output 483 contributions from these processes are shown in table 4, assuming an electromagnetic calorimeter with the same rejection power against jets faking photons as detailed in section 6 above. Because of the large signal to background ratio NS/\/(NB+NS) can be used as a crude measure of the statistical significance of the expected signal: 3.5 at mH=80 GeV/c2 and 3.0 at mH :140 GeV/c2. It should be noted that the bli background has large uncertainties similar to those associated with the jet background to the unaccompanied H->yy. Also NB depends linearly on the width of the mass bin needed to contain the signal. It has recently been brought to our attention [12] that W bosons from the decay of top quarks produced in association with a Higgs (the process gg->tH{) might be expected to more than double the signal. 8. Conclusions A superb electromagnetic calorimeter with a resolution of AE/E = 2%/N/E GB 0.5% would be able to detect a very significant signal from standard model Higgs bosons in the mass range l00 References [1] See, for example, S. L. Wu, Proceedings of the ECFA workshop on LEP200, vol II, CERN 87 -07 Z. Kunszt and W. J. Stirling, Phys. Lett., 242B (1990) 507 [2] D. Froidevaux, these proceedings [3] C. Barter et al, Proceedings of 1987 Berkeley Workshop [41 Z. Kunszt, these proceedings [5] F. E. Paige and S. D. Protopopescu, ISAJET version 6.24. ISA} ET is a Monte-Carlo event generator using the parton shower technique to simulate QCD and QED topologies beyond leading order. [6] E. Berger, E. Bratten and R. Field, Nucl. Phys. B239 (1984) 52 Of the two diagrams giving large contributions to the prompt di-photon production cross-section in the kinematic region being considered only the quark-antiquark annihilation process is coded in ISAJET 6.24. In order to generate di-photons from the gluon—fusion box diagram we have inserted the matrix element from Berger, Bratten and Field into the relevant ISAIET routine. [7] BCDMS tit with A=l90 MeV, described in P. Harriman, A. Martin, R. Roberts, W. Stirling, preprint DTP 90-04 (April 1990) [8] P. Aurenche and L. Camilleri, private communication. The comparison is done using the same structure functions in ISAJET (Duke and Owens) as used by Aurenche et al. See also H. Baer and J. Owens, Phys. Lett., 205B (1988) 377, and M. Werlen, these proceedings. We have also directly compared the cross-sections for the annihilation and box diagrams obtained using ISAJ ET with those obtained by Aurenche et al. The agreement is excellent. [9] See H. Plothow-Besch, these proceedings. [10] D. Dicus and S. Willenbrock, Phys. Rev., 37D (1988) 1801 [11] Z. Kunszt, these proceedings; also R. Kleiss, Z. Kunszt and W. Stirling, preprint DTP 90-54 and ETH-TH 90-29 (August 1990) [12] W. J. Marciano, private communication. OCR Output »/s=16TeV 5 1Qz% DD->H+XH-Mr (gluon fusion) 10 1 1, pp->WH+X H—>·yy.W·—>ev,pu 10 80 100 120 140 150 M,. (GeV/cz) Figure 1: 0‘.Brf0rH—>yy (U) Signal ( b) intrinsic backgrou (relatively normalized). gg T 1*-r_"—*__` s_{__k_ r' 0 0.5 1 1..5- 2.5 5 5.5 4 4.5 0 0.5 1 1.5 2 2.5 5 5.5 4 4.5 M¤x(|n,|,|n21) M¤><(I¢;,I,In2I) OCR Output Figure 2:Rapidity of photon with largest absolute rapidity 485 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 P; (GeV/c) P: (GeV/c) P; (Gcv/c) 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 P1 (GeV/c) P5 (GeV/c) P} (GeV/c) (2;) signal (0) amimzamm diagram (ct bax diagram Figure 3:Transverse momentum distributions of photons b ( ) 300 t. (G) §QQ fc) JOO L id) 300 L 200 200 200 200 100 100 *00 *00 { 5 ag ' ;-¤,,I %7.5 100 102.5 %7.5 100 102.5 %7.5 100 102.5 %7.5 100 102.5 Mus, (Gov/ct) Mu, (0,v/c*) Moss (G•V/c') Moss (GeV/c ) Figure 4: Reconstructed mass plots for Higgs boson, mH=100GeV/c (a) smeared by: calorimeter energy resolution of AE/E=2 %/ 1/E$0.5 % (b) smeared by: calorimeter energy resolution of AE/E = 7%/ 1/E $1 .0% (c) smeared by: pileup energy from, on average, 10 interactions (d) smeared by: loss of knowledge ofthe vertex position (0’,.¤,=55 cm) 486 OCR Output 487 ""`“"" ‘··· 210*1 .--`___ _, g f-- —‘ - - \ 2 103 g 1 jets 10 2 TO ""NR I;. ...¤.‘....? ·'"H·".."""`”· yfromjets _1 F after all cuts 10 glued K0 | _2 10 ,.-.-.-.-.-.———------. _.-. 1°`E_ {’L.°{Rli§Z2'...+ x+brem) 1Q ...... 1 O k -1 Prompt 7 (including bromsstrohlung) 1 O - - —· Inclusive 1r ·····-···· Jet background after isolation -· -·- Jet background after isolation and n' rejection 10 20 30 40 50 60 70 80 90 100 80 90 100110 120 150140 150 p. (GeV/c) Mass (GeV/c') Figure 5: Inclusive do/dp; (/11/<2) Figure 6: da1dm,,,after kinematic cuts AE/E= a/x/E®0.5% AE/E = 0/t/E€B1.0% JS=16TeV, /Ldt=10p¤·’‘ JS==16TeV, fLdt=10pir’ ' / H 1 0 m,,==1OOGeV/cz i 1 0 m,,=100GeV/cz 9¤> i ` ` 1 ;» s ·‘’‘1·~·- * .;» 8 _ · · T N NTITHTS '-` fj i` _ .-` ·- '-N-V-·—`—-~`°`_""·—!-·-.-____ _ ·-·••—V•·····‘V···—·—-—·-1-.. -,__4i 4 Q. —-•— Calorimeter 4 I. ——•— Calorimeter •- — Calorimeter and pileup • - Calorimeter and pileup Calorimeter, pileup and o’,,.=1.0cm -·•—· Calorimeter. pileup·¤nd o,,,=5.5cm -•·· Calorimeter, pileup and o,,,=5.5cm (After removal of jet background) (After removal of jet background) 0123456789lO OOl234567891O (cr) ¤<%) (bl ¤<%) Figure 7: Signqicance of signal seen from Higgs boson of mass 1OOGeV/cz using calorimeter with resolution function AE/E =c1/ 1/E $12%